Lionel Aufauvre

New Trends for Pyrotechnic Automotive Safety in the European Union

In the European Union (EU) pyrotechnic articles are subjected to comply with national regulations in addition to a series of EU Directives. In order to harmonize regulations in the EU, the placing on the market of pyrotechnic articles is going to fall under the scope of a new European Directive. Among these articles, one finds pyrotechnic components of automotive safety equipment such as gas generators or igniters. In the very fast growing market of automotive safety industry, regulations might be perceived as non-technical barriers to innovation in the field. Conversely, through innovation arguments, industries sometimes try to promote specific cases of exemptions to comply various regulations. In a broad approach, we examine both regulation and industrial recent repercussions in the field of pyrotechnic devices for automotive safety, as these points of view face each other too often. Considerations regarding design, transport classification, approvals, safety features, environmental issues and treatment of end-life waste disposal are provided along the life cycle of the products. We enlighten needs in term of harmonized standards and technical procedures to answer regulation requirements. Such needs bring new perspectives and make room to various stakeholders for possible and efficient developments.

Introduction

More than three decades ago pyrotechnic articles appeared in automotive industry. Pyrotechnics entered first in our car by the steering wheel as energetic component of driver inflatable restraint system commonly known as airbag. This move started in the United States and then reached Europe, mainly through Germany and Sweden where it was proposed as optional equipment for luxury cars at first. But rapidly, airbag flourished in all car manufacturers and was implemented on regular cars as a standard marketing argument for selling new car models. In the mean time, the number of such pyrotechnical equipment multiplied in each vehicle as they showed their efficiency to save lives. After the airbag for the driver came additional passenger, side, and curtain airbags and other automotive pyrotechnic systems such as seat-belt pretensioners (see Figure 1). The tendency turns far away from the time when some people thought unsafe to carry explosive loads on board of a car in motion. Surprisingly, nowadays customers don't pay any attention to driving their car with hundreds of grams of energetic materials distributed around the passenger compartment. However, in parallel to those developments to safer environment for car passengers, it was known that those articles were potentially dangerous by nature [START_REF] Michot | Evaluation of the hazards presented by pyrotechnic devices for public use: consumer fireworks and protection systems for cars[END_REF]. Several risks, mainly due to the presence of energetic materials based hazardous components have to be considered: these risks entail unexpected basic explosions and toxic emanations during normal operation of such systems. Moreover, dangers are present on the whole value chain of automotive pyrotechnics devices, comprising equipment manufacturing, transportation to car makers, operations during the car assembly and eventually all along equipment life and even during end life disposal. Safety and security aspects were then with good reason carefully regulated in different countries.

Situation in the EU

In Europe for the moment these pyrotechnic articles (and many others) fall under different national regulations and approval procedures (e.g.: Decree n°90-153 in France [START_REF] Aufauvre | French Approval Procedures for Pyrotechnical Automotive Safety Equipment[END_REF], Explosives Law in Germany…). Even if, there are similarities between the tests procedures applied in each country, manufacturers of such systems have to pass different approvals to trade their articles in different countries. The test procedures usually consist to submit the items to different stresses (vibrations, drop, impact, heating…). Although the way to apply these solicitations is somewhat different from one country to another, the tests are pertinent enough to detect lack of consistency.

Soon the situation is going to be harmonized to achieve the free movement of pyrotechnic articles in the internal market of the EU and at the same time ensuring a high degree of protection of human health and safety of consumers. Similarly to what have been done for explosives for civil uses (Directive 93/15/EEC of 5 April 1993) a new Directive [3] is about to cover the placing on the market of pyrotechnic articles.

Cases study

Here we discuss cases encountered when testing airbag inflators or other pyrotechnic articles for automotive safety in the frame of the French approval procedure. We believe that other countries have similar experiences and that detailed results have to remain in confidence. We intend to show the need of regulations and test procedures and how they conduct the manufacturer of equipment for motor vehicles to make safer devices. That has to be achieved not only for "final users" (i.e. car drivers) but more importantly for workers that handle these pyrotechnical items at a low level of integration in inert protective shielding systems.

When exposing airbag gas generator to an external fire some "non-mature" models have shown tendency to break and generate projections at significant distance. That was a clear remainder for those who have forgotten what can happen if an energetic material is placed inside a metallic case under certain conditions. The manufacturers answered those pitfalls by making thicker body case and by crimping and swaging assembly allowing improvement of the mechanical/thermal resistance and relating stress compatibility.

Missile behaviors were also observed as gas ejected through holes may create a significant thrust. In this case it is the whole inflator which is propelled, basically like a rocket, as usually same components produce same effects. Exhausts designed with radial distribution to insure a "neutral thrust" when gases are generated were rapidly adopted as an ideal solution.

When operating, airbag inflators and more generally pyrotechnic devices function primarily as gas generators, through some kind of combustion process. The combustion gases emitted are then converted in several mechanical actions or used directly. Toxicity of the resulting emanations is an issue in passenger compartment, especially due to confinement of a passenger car environment. Early gas generating compositions consisted in mixtures of potassium nitrate, sodium azide and silica, which mainly produce nitrogen gas in a chemical reaction (see Figure 2).

2 NaN 3 ------> 2 Na + 3 N 2 (g) K 2 O + Na 2 O + SiO 2 ------> alkaline silicate 10 Na + 2 KNO 3 ------> K 2 O + 5 Na 2 O + N 2 (g)

Figure 2: Decomposition of sodium azide

The toxicity of side products generated by decomposition of sodium azide in the reaction process as well as the intrinsic toxicity of sodium azide itself made the technology shift to what is known as "hybrid gas generator". In such a system, an inert gas is stored under high-pressure in a tank and the pyrotechnic component reduced often to a simple initiator is used to break a rupture disk that releases the gas. But the weight of these inflators due to high-pressure vessel made of stainless steel can present as a significant drawback when large amount of gas is required. Hence, the late trend is to return to the use of propellant at least less toxic as early formulations and with formulations developed to reduce combustion related toxicity as well. Regarding transportation of these pyrotechnic equipment the automotive industry requests to keep constraints at a minimum, in order to cope with the 'zero delay' delivery concept prevailing in the automotive industry. But, by nature of some of their components, these devices have to be viewed as dangerous goods regarding transport regulations. Early consideration of these products concluded to consider them as explosive objects falling in the Class 1 (Explosives) of the United Nations (UN) classification for dangerous goods (see Figure 3). Compromises were found later, under particular conditions, for a classification in Class 9 (Miscellaneous dangerous substances and articles), under UN number 3268 designated as "air bag inflators, or air bag modules, or seat-belt pretensioners". The development of containers with metallic perforated sheets or meshes providing containment of potential projection without confinement of gases released played an important role for the acceptation of this classification. These containers are essential to allow storage in car manufacturing assembly lines and are also designed to be used as handling devices to avoid unnecessary manipulations in workshop.

Testing procedures

As the automotive equipment technology is moving fast, pyrotechnic items used for safety also evolve quickly and appear now in various systems (e.g.: protection to pedestrians or equipment for motorcycle riders). Moreover, similar items find applications in other field that may not have the same capacity to develop the technology. We can mention as example the "avalanche airbag system" for off-track skier protection, which avoid trapping them under snow. The real need for harmonized test procedures in Europe should soon be covered by the implementation of a new Directive [3], which should indeed cover these articles as well as other pyrotechnics. Similarly, there is a parallel need for test procedures to be able to correctly evaluate new devices.

More and more, considerations to satisfy all test criteria for exclusion of automotive components containing energetic materials from the UN Class 1 are taken into account as soon as the conception phase of the item. Whenever it is possible, this is achieved by containment of all effects inside the object or at least by strong limitation of external effects such as exhaust of hot gas, loud noise, wall heating…

Recycling

Fortunately for the occupants, the majority of pyrotechnic automotive safety systems never operate during the lifetime of the vehicle. Then there is another issue. Process to recycle cars consists to compacting and shredding usually, which can create troubles when applied to energetic materials containing components. In addition to the hazards of explosion that can damage recycling equipment, the dissemination of toxic propellant like sodium azide endangers workers and environment. There are currently no cost-efficient solutions as re-use of second-hand airbags is not easy and not even recommended. Operating all pyrotechnic devices at the end of their life may not be ideal either [START_REF] Marlair | Toxicity issues pertaining to burning pyrotechnics[END_REF]. Dismantlement of such devices from the cars requires special care and particular cautions for handling and storing operations before further treatment.

Then regarding environment protection, the issue of treatment of pyrotechnic articles withdrawn from wrecked vehicles is growing, since this aspect was not really considered until recently. There are no reasonable industrial ways for safe disposal and, most often, devices are operated before dismantling.

Conclusion

It is now well established that airbag systems contribute to decrease the number of casualties in car accidents. The technology based on pyrotechnic components has shown its utility in safety automotive systems where a short reaction time is required. But with the multiplication of such equipment in vehicles and of similar items in other fields, pyrotechnic articles are promised to new developments. However, as long as energetic materials will be part of these items, special attention and careful evaluation will have to be taken. In particular consideration of "side safety and environmental issues" on the whole life cycle of such products would gain be putting on the scene more in advance, at the design stage, for more easy and sustainable development.

Figure 1 :

 1 Figure 1: locations of pyrotechnics in a car (steering wheel, dashboard, doors, seat-belts…)

Figure 3 :

 3 Figure 3: UN transport classification for dangerous goods


Guy Marlair

Richard Turcotte

Queenie S M Kwok

Ruddy Branka

Toxicity issues pertaining to burning pyrotechnics

We all know that normal operations with pyrotechnic compositions or other energetic materials, apart from the desired effect (e.g.: controlled blast from high explosives, propulsive power resulting from propellant gas pressure, various visible or sound effects from fireworks...) lead to the release of various products (gases, vapours, aerosols) in the environment, in relation with the chemicals, the reactions involved and some physical parameters.

Although discussed from time to time by experts, and contrary to the case of 'conventional' fires [1], toxicity and environmentally related questions associated with burning pyrotechnics, have received far less attention than they actually deserve. Therefore, this paper supports an analysis of our current understanding of the sole toxicity problems (acute toxicity, sub-acute toxicity concerns...) emerging with all types of burning pyrotechnics, at the light of what has been established to address 'normal' fires in built environments. The paper provides an analysis of the regulatory context, lessons from past accidents, typology of chemistry and reactions of pyrotechnics, and some contribution to the analysis is supported by experiments on smoke powders, one significant family of products belonging to pyrotechnics. Eventually, a discussion is proposed to envisage pathways to go further in learning on those important issues.

Introduction

Pyrotechnic compositions present challenging issues in many aspects. Combustion related issues and safety considerations are no exception, and even in some well known cases look like controversial issues. For instance, the availability of first generation air-bags systems was considered as a major step in the reduction of car crash impacts on passengers. However in the same time, both intrinsic and non intrinsic combustion related toxicity issues have been raised, due to the type of gas generating energetic materials primarily used for their development, namely sodium azide [START_REF] Aufauvre | New trends for the Pyrotechnic automotive Safety in the European Union[END_REF] [START_REF] Pradère | A new composition for gas generation in air bag systems[END_REF]. Considering pyrotechnics in a more global scope, the extreme diversity of their applications (pyrotechnic compositions used in display and consumer fireworks, propellants and powders, 'special effects' systems (like distress flares, gas generators, smokes of all sorts), pyrotechnic devices for the automotive industry...) is by itself very challenging for coping comprehensively with all safety-related issues.

The analysis of toxicity issues proposed in this paper was motivated from the lead author's primary scientific background; that is 'conventional fire' safety. The so called 'conventional fires', are all those fire involving materials that burn by reaction with air in the socalled diffusive (laminar or turbulent) mode. They represent a large fraction (say 99%) of all fires taking place in any type of built environment. Fire safety science, and related fire engineering practice, were developed as early as in the late 1890's, when for instance, the NFPA (National Fire Protection Association), a nonfor-profit organization solely devoted to reducing all types of fire threat (primarily of thermal nature) started to develop standards and codes. As compared to current knowledge in the field of pyrotechnics (those materials sometimes referred to as 'low explosives'), toxicity fire science constitutes by now a well advanced knowledge, and as a result, more interactive processes between scientific communities covering fire science, and those covering safety related issues of explosives, and pyrotechnics of all sorts is thought highly desirable [START_REF] Marlair | Energetic Materials and the fire problem[END_REF]. This view is expressed despite significant differences in the reaction processes that are involved with burning pyrotechnics comparatively to conventional fire. This paper is an effort to contribute to such a process.

With the guidance brought to us by fire scientists on combustion-related toxicity issues, our purpose is therefore:

to review what is the current knowledge on the matter regarding pyrotechnic compositions of all sorts, when reactions taking place and liberating chemical species do not lead to mass explosion, to review how those issues are currently handled by regulations or other means in some applications and provide some analysis on how to progress to explore capabilities of some experimental equipments (e.g. the US Fire Propagation Apparatus (FPA) so called 'Tewarson' Apparatus in France [START_REF] Astm E | Standard Test methods for Measurement of Synthetic Polymer Material Flammability Using A Fire Propagation Apparatus[END_REF], other more conventional laboratory calorimetry techniques) to provide information on toxicity pertaining to burning pyrotechnics to discuss on how we should try to progress in the field in future research efforts.

Combustion-related toxicity of energetic materials and regulations

Control of the toxicity threat from regulation is currently very limited, if actually existing at all for pyrotechnics: Four main reasons for this situation can be quoted: a) Combustion toxicity is by no means an intrinsic property of any material, as recalled long ago by Babrauskas [START_REF] Babrauskas | Toxic Hazard from Fires: A Simple Assessment Method[END_REF]. As an example, in the context of the Canadian regulatory scene, carbon monoxide plus nitrogen oxides emitted by basting agents or high explosives are referred to as fumes by the explosive industry. A classification containing three classes of those materials have been established according to specific test conditions [START_REF] Mason | Methods for Evaluating Explosives and Hazardous Materials[END_REF] on the quantity of fumes produced. Only class 1 explosives (limiting the emissions of fumes to less than 22.6 L/kg of cartridge of given geometry) should normally be used in underground applications. On the European side, long term collaborative research ended up with the implementation of national limits for a toxicity index taking account of CO and NOx emissions based on the application of the standard EN 13631-16 [START_REF]Explosives for Civil Uses -High Explosives: Part 16 Detection and Measurement of toxic Gases[END_REF] for same usage (underground mining).

By comparison, a similar situation appears regarding the control of toxicity issues in accidental 'normal' fires. Regulators have often felt reluctant in the past to set regulations for the control of the non thermal fire hazard, with a few exceptions, like in the transportation sector (aeronautics, railways), where prompt evacuation of occupants of concerned enclosures (rail cars, aircraft cabin) are not a potential emergency response, in case of a fire. As an example of this, the French subways and railways operators require that materials used in rail cars fulfil requirements defined in combined French standards [11], [START_REF]Fire Test -Analysis of gaseous effluents -Part 1:Methods for analysing gases stemming from thermal degradation & Part 2:Tubular Furnace thermal degradation method[END_REF]. As a result of numerous studies of the kind carried out on both side of the Atlantic Ocean, regulators have developed requirements expressed in terms of maximum threshold values for the sum of [CO + NO x ] for mining applications.

To our knowledge [START_REF] Michot | Toxicity of Smoke Pyrotechnics[END_REF], limitation of toxic yields from burning pyrotechnics exist only for air-bag inflators. In that case, the toxicity problem was an issue identified in the early stage of development of such safety car components, due to both inherent toxicity of sodium azide, the first gas generating material that was used, and from combustion / decomposition related toxicity.

Further reduction in combustion toxicity obtained from use of new blends of chemicals such as compositions with complexes of transition metals [3] [14], together with other performance targets such as increase in gas production rates, is still in the current research agenda of developers [START_REF] Tomiyama | Development of non-toxic propellant for the automotive industry[END_REF]. However, target limits are driven by the automotive industry proprietary standards, and thus, due to competition, test data on toxic emissions from the various pyrotechnic compositions in use are not easily made available in the public domain.

We might have to face in the near future an increasing societal demand, in particular impacting the firework industry, for knowing more about actual concerns that might arise from repeated exposures of diluted smoke in the environment of the workers (professional of display fireworks) and of the public. This could, in turn, initiate some move from the regulatory scene in this sector.

Fire Toxicity: brief overview of state-ofthe-art

About three decades of research have been dedicated to the study of toxicity of fire effluents. In this time, it has been recognized that the bulk of fire victims generally die from toxic smoke inhalation rather than from thermal burns (Alarie [START_REF] Alrarie | Toxicity of fire smoke[END_REF]). Prominent researchers in the field during that period of time have been Hartzell [START_REF] Hartzell | Combustion Products and Their Effects on Life Safety[END_REF], Purser [START_REF] Purser | Toxicity Assessement of Combustion Products[END_REF], Alarie, Tsuchyia [START_REF] Tsuchiya | Significance of HCN generation in fire gas toxicity[END_REF], Levin [START_REF] Levin | New research avenues in toxicology: 7-gas N-Gas Model, toxicant suppressants, and genetic toxicology[END_REF], Baud [START_REF] Megarbane | Origin and treatment of intoxication from inhalation of fire gases -An overview[END_REF], Gann [START_REF] Neviaser | Evaluation of Toxic Potency Values for Smoke from Products and aterials[END_REF], and some others. Recent overviews are available that correctly summarize current knowledge as well as workable tools for use in toxicity risk assessment (see also the recent international standards being produced by ISO TC 92 SC3, progressively replacing the old reports series produced in the late 80's [START_REF] Iso Tr | CHAF work Package 9: Instrumented full-scale testing -D9-3 and D9-4:Test results and analysis[END_REF]).

From their work and findings, the following is of interest, in terms of knowledge transfer to the scientific community of pyrotechnics:

Acute toxicity in fire always results from multiple components exposure that superimpose to other environmental parameters (temperature, stress, health conditions of exposed people..), Figure 1 expresses the Haber's rule often considered for individual toxic fire component stating that a given effect (e.g. lethality) is a function of the dose (time x exposure) received. Although hundreds of components are emitted in fires, a limited number of them are responsible for actual acute toxicity threat, that can be classified into : a) asphyxiant, or narcosis-producing toxicants (CO, HCN, CO 2 , limited O 2 ) b) sensory or pulmonary irritants (NO X , SO 2 , HCl, HBr, aldehydes, particles...) c) toxicant exhibiting other or unusual effect (e.g. neurotoxics, carcinogen effect...) In most cases, CO levels were found high enough (in terms of carboxyhemoglobin -COHb-in blood samples from the bodies) to be assumed as the primary cause (if not the unique cause) in fire deaths occurring in built enclosures; rare other situations have been identified where HCN or SO 2 [1] played the main role in 'conventional fires' casualties.

To a reasonable approximation in most cases, the effects of major toxic components may be considered as additive for situation of interest with asphyxiants and irritants, although the real effects comprise more complex synergisms and even in some cases antagonistic effects [20/21]. These latter results have led to the development of the fractional effective dose (FED) model, that expresses this concept in its simple form according to equation (1):

n h FED = X Z i = l t, C, (Eq. 1)
Where in the summation, any Q term stands for the concentration of toxic species i taken into consideration, and (Ct)i stands for the critical dose related to that species i for a given effect (e.g. lethality). When the FED value reaches 1 in a given scenario, the toxic effect intensity is assumed to be obtained. Considerations on the validity of this type of equation for various types of exposed subpopulations have been reported by Hartzell [START_REF] Hartzell | Engineering analysis of Hazards to life safety in fires: the effluent toxicity component[END_REF]. Equation ( 2) is the simplest form taken by the FED model when assuming the toxic threat is limited to CO + HCN. Equation ( 2) also reflects the fact that the dose-effect relationship followed by the HCN species do not actually follow the Harber's rule, concentration level 'weighing more importantly' than exposure time in that case.

In contrast, equation ( 3) is the more complex but still workable equation that may be used by fire engineers to analyse the risk of incapacitation in built environment that can arise from the combination the following irritant species:

[HCI] [HBr] [HF] [SOJ [N0 2 ]
"• "-""i-+ "r;-+ "s~+~B-+ ~E-+ r l!CI r HBr r HF r SO; r NO:

[acrolein] [forma Idehjde] forsituati t s, (Eq. 3) The concept of lethal potency (that is the toxicity of the smoke (gases +aerosols) from a specimen of material or product, taken on a per unit-specimen-mass basis, depicted by the symbol 'LC 50 ') has been developed to account for the concentration which will be lethal to 50% of the exposed subjects. LC 50 's are accessible from experiments including bioassays using animals as well as through estimates derived from lab-scale combustion experiments on materials, and from use of models (eg. ISO 13344 [START_REF]Estimation of the lethal toxic potency of fire effluent[END_REF]), based on existing animal test data, according to measured concentration of toxic species in the smoke environment. Figure 2 gives an overview, in arbitrary units, of the toxicity issues pertaining to conventional products emitted in conventional fires (gases and smoke), confirming their toxic potency and providing some ranking between toxic species. Figure 2 also illustrates that "actually supertoxic" fire effluents, that were in focus in the past in fire research are extremely rare. This is indeed one of the interests of the LC 50 concept (when coupled with bioassays), that allows rapid identification of combustionrelated extra-ordinary toxicity issues, during early stages of new materials or products development [START_REF] Neviaser | Evaluation of Toxic Potency Values for Smoke from Products and aterials[END_REF]. Very few problems of this kind were reported in the literature in the past, like the cases known exceptions regarding PTFE smoke particles and an organophosphorous caged compound identified in a burning test involving a fire-retarded polyurethane foam [START_REF] Purser | Recent Development in understanding the Toxicity of PTFE Thermal Decomposition Products[END_REF].

However, unpublished cases may have also occurred during R&D work performed by the chemical industry ( [29]) Indeed, we have currently no precise idea on how 'pyrotechnic smoke' (limited to the aerosol components) is ranking relatively to the other products listed in Fig. 2. Last but not least, it has been established (e.g. by Babrauskas [START_REF] Babrauskas | Fire Safety Improvements in the Combustion Toxicity Area: Is there a Role for LC 50 tests ?[END_REF]) that Lethal potencies of 'conventional fire' smoke doesn't vary much, contrary to rate of smoke production depending on materials and scenarios, which in turn makes the real difference. That is why fire scientists are focusing on obtaining basic fire data such as mass burning rate per unit area and yields of combustion products emitted (in mg/g) to characterise 'source terms' of non thermal damage potential, in addition to estimate of some kind of critical toxicity value for species of interest. Many searchers have produced such data for various materials. A compilation of such data for burning chemicals was recently published by Tewarson & Marlair [START_REF] Tewarson | Liquids and Chemicals[END_REF].

Analytic analysis from chemistry of pyrotechnics

Pyrotechnics highly differ from classical combustible materials in many ways, and thus a careful examination and comprehension of their chemistry and reaction modes under normal use or accidental scenarios are needed to identify and evaluate toxicity issues relating to species emitted in pyrotechnics gases and smoke.

One of the basic differences is that most of the time, if not in all cases, pyrotechnic compositions intimately mix combustible materials (carbonaceous, sulphur, phosphorous, metals, others...) with oxidisers (nitrates, perchlorates, chlorates...). Thus, the community of pyrotechnics knows very well, from information available in the references [START_REF] Shimizu | Fireworks -The Art, Science and Technique[END_REF] to [START_REF] Hardt | Pyrotechnics[END_REF], the high variety of possible pyrotechnic compositions according to applications (industry of fireworks, distress signals, propellants for military or civil use, special effects). As a reminder, when coloration of the effect is the issue, the chemistry of the composition will vary according to desired color and luminous intensity. Potential chemicals that may be used (as an example!) are indicated in table 1.

Table 2 was prepared from ref. [START_REF] De | CHAF Worl Package 9Instrumented full-scale testing -D9-3 and D9-4: Tests results and analysis[END_REF] to [START_REF] Fujiwara | Characterisation of Environment Toxicity for Combustion Products of Fireworks[END_REF]. It lists and classifies products emitted that may contribute (with highly varying weights) to the overall potential toxicity arising from those products when burning, according to typical pertinent scenarios.

What do we know so far from accidents and testing ?

Regarding the fireworks industry, statistics recorded by the NFPA [START_REF] Hall | Fireworks-related Injuries, deaths, and fires[END_REF], as well as other information sources from recent well known accidents (Enschede, NL, 2000 [START_REF] Yanlik | Enschede, Final report -Final Consideration, rapport Enschede[END_REF], Kolding DK, 2004 [START_REF] Marlair | The Fireworks Explosion and Fire in Kolding, Denmark, November 2004[END_REF] [START_REF] Kriger Andersen | The firework Accident in Kolding-3 November 2004: What have we learnt from it ?[END_REF] essentially stress that most (if not all) victims are the results of burns and blast effects in case of accidental mass detonation, or possibly, in some cases, from the consequences of physical impacts of projectiles. However, in both mentioned worst-cases, some medical treatment has been required for a few inhabitants leaving close to the premises or firefighters just after the accident. To our knowledge, relating symptoms did not apparently end up for those patients with persistent troubles.

In addition, more scientific feedback was made available as the aftermath of a measuring campaign implemented during and just after the accident of Enschede [START_REF] Mennen | Vuurwerkamp Enschede: Metingen van Concentraties, verspreiding en depositie van schadelijke stoffen: rapportage van het milieuonderzoek[END_REF]. The study consisted in taking samples on the day of the fire and on the following days to perform analytical measurements of toxic/pollutant species. The results, which refer to three different phases for the data acquisition provides clear indication that a number of species were present in concentrations that significantly exceeded socalled 'long term acceptable limits' quoted for a comparison in the report. According to that report, the bulk of the substances and chemical elements at the origin of the gaseous and solid emissions are as follow (table 3) Other type of pyrotechnic materials would deserve further consideration as regards the combustion related toxicity issue. For instance, normal use and accidental burning of propellants based on AP/HTPB systems essentially raises the question of HCl emissions. Although some work has been done in the field [START_REF] Keaffaber | Evaluation of fireworks emissions sampling strategies[END_REF] [37] [START_REF] Turcotte | Thermal analysis of black powder[END_REF]..., we are still lacking consolidated data on burning behavior of black powder, an essential constituent of lifting and bursting charges in fireworks devices. Within the automotive industry, the initial toxicity issues relating to sodium azide and related decomposition products have somewhat shifted to the control of other types of toxic species according to propellants under development and from controlling oxygen displacement by N 2 generation Finally, another type of pyrotechnic compositions, those in use for generating "more or less buoyant "smokes" (e.g. screening effects for military applications), may cause well identified potential concerns regarding toxicity . At first, smoke compositions have been reported to often contain inherently toxic products [START_REF] Hardt | Pyrotechnics[END_REF]. In addition, acute combustion-related toxicity have been recently proven by a detailed study on given smoke compositions [START_REF] Hemmilä | Evaluation of Toxicity and Irritation potency of a white buoy smoke for marine use[END_REF]. In the latter case, products of concern were essentially organic compounds that also raise the carcinogenic risk issue. Survival fractions of such organic compounds, that much often present irritant properties, are generally very limited in temperature environments exceeding 500to700°C [START_REF] Terril | Toxic Gases From Fires[END_REF].

Experiments on smoke powders

Test materials

Two different smoke powders consisting in ternary mixtures containing starch and lactose as fuel components and potassium nitrate as an oxidizer have been supplied to investigate the potential toxicity concerns arising for their use as "clean smoke" generators.

Such compositions are currently in use by the Fire Services in Switzerland and France for the control of smoke venting systems in buildings. The characteristics of the two test smoke powder samples used in the test series are indicated in table 5.

Experiments conducted by INERIS using of the Fire Propagation Apparatus 5.2.1 The FPA or Tewarson Apparatus

A Tewarson calorimeter (see fig. 3) was commissioned in a dedicated laboratory by INERIS in 1997. Designed in its early configuration as soon as the mid 1970s (Tewarson and Pion, [START_REF] Tewarson | Flammability of Plastics, I-Burning Intensity[END_REF]), the current version has significant advantages, having benefited from more than 20 years of development and technical improvements. Associated test protocols give access to information on fire related phenomena of a qualitative nature (visualisation of product specific phenomena, or characteristic flame colour changes etc.) as well as of a quantitative nature (rate of heat release, mass loss, smoke opacity, etc.) that can be obtained for a large variety of materials. The equipment has received more official recognition by standardization bodies like ASTM and NFPA [START_REF] Astm E | Standard Test methods for Measurement of Synthetic Polymer Material Flammability Using A Fire Propagation Apparatus[END_REF], and has quite recently been added in the limited list of equipment that have been recognized capabilities in the field of fire toxicity issues by ISO TC92 SC3 (Technical Committee regarding Fire threat to people and the environment [START_REF]Guidance for assessing the validity of physical fire models for obtaining fire effluent toxicity data for fire hazard assessmen -Part 2: Evaluation of individual physical fire models[END_REF]).

Aluminum support Cylinder

Research work devoted to the exploration of the potential use of the equipment for other goals than learning on the fire behavior of polymeric materials [START_REF] Marlair | Effect of the Generic Nature of Polymers on their Fire Behavior[END_REF] has been the main target with the use of the apparatus in Europe [START_REF] Marlair | On-going Experimental Fire Research and Testing in France using Test rigs Derived from the 'Tewarson Apparatus[END_REF].

Preceding experience with the equipment at INERIS regarding evaluation of the hazards presented by energetic materials comprises: a) the fire behavior of organo-phosphourous pesticides [START_REF] Marlair | Experimental Evaluation of the Fire Hazard of Organophosphorous insecticides by use of various test methods[END_REF], b) the evaluation of toxic emissions of electrolytes for large electric capacitators, c) the analysis of the decomposition processes of nitro-cellulose based archive films and d) the evaluation of toxicity issues presented by mixtures containing incense /oxidizers mixtures. Moreover, fire-induced toxicity properties of chemical additives is also in INERIS research agenda with this apparatus [START_REF] Chivas | Smoke toxicity from combustion products based on Polymers containing flame retardant additives[END_REF]. At last, quite surprisingly, the inventor himself contributed to the evaluation of the potential use of the apparatus in the area of energetic materials by characterizing the fire-enhancing properties of different oxidizers [START_REF] Buc | Development of an Enhanced Classification System for Oxidizers[END_REF].

Experimental results with Smoke Powders

Table 6 summarises the main results obtained from tests under controlled combustion conditions, representing well ventilated fire conditions, in the Tewarson apparatus. Samples weighed some 80 g and were distributed in circular glass pans (88 mm in diameter). Ignition was obtained from a pilot flame without use of the external heat flux system see figure 4). From those results, it can be noticed that a significantly faster combustion process is observed from the mass loss rate measurement leading to a specific rate of combustion of some 400 g/m 2 /s with the powder SP2, containing 45% KNO 3 against only 140 g/m 2 /s in the case powder SP1 only containing 40% of KNO 3 .

Regarding the emissions, as expected from the low temperature of the combustion process, which characterises most smoke producing pyrotechnic compositions presenting obscuring capabilities, a number of irritant species are produced in such quantities that the toxic hazard assessment requires more in-depth analysistaking into account practical scenarios of use-to conclude on actual dangers relating to the proven toxic potency revealed from the tests. A TA Instruments Q-1000 differential scanning calorimetry (DSC) was used to study the thermal behaviour of the same smoke powders in air and nitrogen. About 1-2 mg of smoke powders were placed in aluminium pans sealed with pin-hole lids. The samples were heated from 40 to 550 °C at 5 °C min \ Experiments were carried out in a dry air or nitrogen purge at 50 cm 3 min -1 .

Comparison of DSC Results for Smoke Powders

The DSC was calibrated for heat flow [START_REF]Standard Practice for Heat Flow Calibration of Differential Scanning Calorimeters[END_REF] and temperature [START_REF]Standard Practice for Temperature Calibration of Differential Scanning Calorimeters and Differential Thermal Analyzers[END_REF].

Experimental conditions for TG-DTA-FTIR-MS experiments on Smoke Powder and relating results

A TA Instruments 2960 simultaneous TG-DTA was interfaced to a Bomem MB 100 Fourier Transform Infrared (FTIR) Spectrometer and a Balzers Thermostar GSD300 Quadrupole Mass Spectrometer (MS). The TG-DTA-FTIR-MS data were acquired simultaneously to study the thermal behavior of the smoke powders and to identify the gases that evolved while the samples were heated.

Equal amounts (5 mg) of sample and reference material (Pt foil) were placed in alumina pans and heated at 10 °C min 4 to 1200 °C in air (50 cm 3 min-1 ). TG mass, DTA baseline and temperature [START_REF]Standard Practice for Temperature Calibration of Differential Scanning Calorimeters and Differential Thermal Analyzers[END_REF] calibrations were performed prior to the experiments.

The FTIR interface consisted of a 5 mm i.d. Teflon tube and a 10 cm Pyrex cell with a 50 mL volume and KBr windows. A quartz microfibre filter was placed at the FTIR inlet. The acquisition rate of the FTIR was one scan every minute.

For the MS analysis, the heated quartz capillary interface was placed near the sample pan, in the TG-DTA furnace. Data were acquired using bargraph scan, from 29 to 300 amu (atomic mass unit) at a speed of 0.2 s/amu. The electron multiplier detector was set at 960 V for acquisition. The MS was calibrated for mass alignment and amplifier signal.

Brief analysis of test results.

The experiments relying on the use of the Fire propagation Apparatus (FPA) (see table 7. ) confirm -if needed-the high degree of polyvalence of such an apparatus to address in a reasonable way thermal as well as non thermal issues regarding building and industrial fires, including atypical combustion processes, provided that the rate of reaction is not to high, and that no significant pressure build-up is taking place. From previous experience achieved by Tewarson himself and by INERIS, we may think that the decomposition is representative of most of effects induced in the 'real world' burning processes. On the materials tested, they reveal the potential for such substances to emit irritant substances such as aldehydes in quantities that have to be taken into consideration, even if they are normally absent in high temperature combustion processes, [START_REF] Terril | Toxic Gases From Fires[END_REF]. The second main information is that the concentration in the oxidizer agent (KNO 3 ) plays a role in modifying rate of reaction as well as yields of species emitted.

The other tests were also useful to identify or confirm that the experimental technique may highly influence the results (at least at lab-scale). The DSC tests (figure 5) did not show much difference in the decomposition behavior of the two smoke powders (contrary to FPA), which may find an explanation in the fact that the heating rate is not representative of 'burning pyrotechnics' like smoke powders. The lack of difference for the two smoke powders may also be due to the much smaller sample size used in DSC measurements: the sample size used in the FPA is at least 4 x 104 times larger than that used in DSC. On the other hand, DSC results (see figure 7) show that air may play a role in the case of smoke powders, despite of the general assumption presented in table 7.

There are also no significant differences observed for the thermal decomposition of the smoke powders from the TG-DTA-FTIR-MS results. Similar to DSC, the low heating rate and small sample size used in TG-DTA-FTIR-MS are probably the causes of this lack of difference. Coupled TG-DTA-FTIR-MS results (figure 8) are more illustrative of the interest of coupling different experimental techniques to investigate such a complex issues as combustion related non thermal damage pertaining to reactive materials when burning. Qualitative identification of species emitted from TG-DTA-FTIR-MS tests reveals how powerful those techniques are to perform relevant screening tests with reasonable time/cost efforts. Next step will be to proceed to further investigation by coupling same analytical techniques to flash pyrolysis technique, which use a high heating rate closer to smoke powder burning process. We have shown from preceding development that burning pyrotechnic toxicity issues do exist, although we may reasonably think that acute toxicity concerns resulting from normal use of pyrotechnics are essentially existing in military applications (eg. smoke powders containing hexachlorohexane... ). However, to get a better understanding on all 'non thermal' issues of burning pyrotechnics, from acute toxicity up to environmental pollution and contamination related problems, more knowledge-based information must be produced in order to provide satisfactory data for analysing adequately those issues and be able to evaluate toxicity related problems for cases of interest.

In particular, likewise for the case of conventional fires [START_REF] Gabler | Unseen hazards in fire-fighting[END_REF] [START_REF] Rechenbach | Fires today: Risks and Protection for Fire-fighters[END_REF], repeated exposure more to sub-lethal doses of pyrotechnics smoke might be of concern. The evaluation of such situations (that occur at least for workers, if not for the public with display fireworks shows, and possibly also with smoke producing pyrotechnic compositions and other applications making use of pyrotechnics) must rely on a more in-depth analysis, by producing suitable new information (from test data, new lessons from experience...).

Due to the high variety of pyrotechnic compositions, the importance of toxicity related issues is likely to vary somewhat according to products and applications, so a case by case approach is probably the best method for addressing properly the question. INERIS and CERL have just started to collaborate in such a direction, by examining (see section 5) experimentally the case of smoke powders.

In the near future, other tests with different compositions will be carried out, in the framework of a commonly supported thesis work, to which the University of Edinburgh (UK) (school of electronics and fire engineering) is also associated. The thesis work aims at developing analytical and experimental procedures to learn more on safety issues pertaining to non explosive burning of pyrotechnics. The importance of toxicity issues is also likely to be highly scenario-dependant: normal uses of pyrotechnics with single or repeated exposures to diluted pyrotechnic smoke may represent one generic type of scenarios accidental pyrotechnics smoke releases of all sorts are the second 'generic' type of scenarios to be treated Subdivisions of both categories of mentioned scenarios will have to be correctly identified (for instance 'high' and 'low' temperature systems, 'in-door' and 'out-door' use of pyrotechnics, accidental burning inside enclosures or in the open..).

Table 7 might serve as a guideline to develop adequate research trying to optimize the findings obtained by fire researchers. This table simply outlines significant differences that can pertain between conventional fires and burning pyrotechnics scenarios. burning of pyrotechnics packaging devices and materials lifting charges ? significantly higher importance, as many of the products during burning of pyrotechnics are released as solids or solidify very quickly with decreasing temperature often to be taken as moving sources species, due to lift charges for many fireworks no pertinent standardized testing tool isolated initiatives existing, however.

The importance of toxicity issues is also likely to be highly scenario-dependant: normal uses of pyrotechnics with single or repeated exposures to diluted pyrotechnic smoke may represent one generic type of scenarios accidental pyrotechnics smoke releases of all sorts are the second 'generic' type of scenarios to be treated Subdivisions of both categories of mentioned scenarios will have to be correctly identified (for instance 'high' and 'low' temperature systems, 'in-door' and 'out-door' use of pyrotechnics, accidental burning inside enclosures or in the open..).

Table 7 might serve as a guideline to develop adequate research trying to optimize the findings obtained by fire researchers. This table simply outlines significant differences that can pertain between conventional fires and burning pyrotechnics scenarios. As indicated in the mentioned table, aerosols must also be taken into account in the analysis.

However the complexity of the analysis of the toxicity issues pertaining to the aerosols emitted in burning processes is illustrated in figure 9, that first explain why 'PM 10 ' (particulate matter below 10 urn) may be of concern. The finer the particles are, the deeper they may penetrate into the respiratory tract up to direct interactions with cells in the lungs. Regarding that issue, new information is needed for both conventional fires and scenarios involving burning pyrotechnics, as indicated in recent analysis by Arntz [START_REF] Arntz | What's that noise ? What's that smell ? It is fireworks[END_REF].

Indeed, in the case of pyrotechnics, high temperature systems toxicity issues are probably more dependant on the size of the aerosols.

Conclusions

The current understanding of combustiontoxicity issues of burning pyrotechnics has been reviewed, with state-of-the art knowledge of related issues pertaining to 'conventional fires' serving as a guideline in the analysis.

From existing -and still very limitedinformation based on testing, past experience regarding normal and accidental scenarios where pyrotechnic materials are burning, acute toxicity issues seem to be limited to a number of more or less well identified cases (devices providing screening smoke for military application, possibly also 'first generations' air-bag inflators making use of sodium azide and other propellants).

However, existing knowledge regarding toxicity related issues of pyrotechnics are far less advanced than in the case of combustible materials burning with surrounding air in built enclosures or in the open. Moreover, studying combustion toxicity issues pertaining to pyrotechnics appears to be more complex due to the much higher diversity in chemistry and combustion processes exhibited by these materials, as compared to normal fires involving common materials.

Therefore, research efforts in the area are highly desirable and they may benefit from some of the engineering tools developed to study more general fire safety issues.

Our experimental contribution to support such an effort regarding the behaviour of smoke powders confirms that powders containing KNO 3 may present sub-acute toxicity issues, depending on scenarios of use.

Our understanding is that generally, those pyrotechnic devices leading to 'low temperature' decomposition or combustion processes, in order to produce special effects like screening are of concern, as they are liable to produce significant amount of organic irritants (like aldehydes) or organic species of specific toxicity (carcinogenic substances... ). These tests have also proven the capacity and the interest of combining experimental techniques so-called 'fire calorimeters' (such as the Fire Propagation Apparatus) to more conventional calorimetry techniques coupled with MS/FTIR systems.

At last, we keep on thinking that closer collaboration between the scientific community of fire science and those relevant to energetic materials would be of mutual benefit (for instance for the development of validated sampling and analytical techniques for aerosols produced by combustion / decomposition processes).

Acknowledgements

The support of the Swiss Institute for Safety and Security regarding the experimental part of this work is gratefully acknowledged.

I

  Figure 1: Dose-response relationship of fires for 2 substances 'A' & 'B': the basic paradigm of fire toxicology (adapted from Pauluhn [24])

Fire effluentsFigure 2 :

 2 Figure 2: Range of toxicity potencies for combustion products as compared to other poisons -(adapted from Hirschler, 1987 [27])

Figure 3 :

 3 Figure 3 : schematic view illustrating the operating principle of the Fire Propagation Apparatus (FPA)

Figure 4 :

 4 Figure 4: Smoke Powder 1 burning in the Tewarson apparatus operated by INERIS

Figure 5 :

 5 Figure 5 : DSC results on Smoke Powders

Figure 6 :IFigure 7

 67 Figure 6 : DSC results on Smoke Powders, repeatability analysis Figures 5 to 7 report on some graphical results obtained on smoke powders with DSC experiments. Comparison of Smoke Powder 2 (45 % KNO3) in Air and in N2 I = 5 °C min 1

  a) TG-DTA; b) FTIR; c) MS results for 5 mg INERIS Smoke Powder 1 heated in air at10°Cmin-1 .

Figure 8 :

 8 Figure 8 : Evolution of TG-DTA/FTIR/MS results for smoke powder 1 (40% of KNO3) according to common temperature range 6. Discussion

Figure 9 :

 9 Figure 9 : inhalation pathways of aerosols according to particle size

Table 1 (from [4]): color-governing chemicals in pyrotechnic compositions

 1

	Chemicals or	Flame color	Light intensity
	chemical element	obtained
	Li	carmin red	intense
	Na	yellow		intense
	K	purple pink	weak/average
	Sr	red		weak/glow
	Ba	green		weak/glow
	CaCl	orange red	intense
	SrOH & SrCl	red		intense
	BaOH &BaCl	green		intense
	CuOH	green		intense
	CuCl	blue		intense
	BO 2	green		intense
	Mg, Al	bright white	intense
	Some	300	different	pyrotechnic
	compositions have also been compiled and made
	available on the web according to the initiative
	coming from the Netherlands [34].

Table 2 : Significant products emitted from by reaction of pyrotechnics (fireworks only)

 2

	type	chemicals emitted
	gases	CO x , H 2 , H 2 S, CH 4 , COS, CH 4 , N 2 , NO x ,
		O 2 , SO 2 ...
	aerosols Al 2 O 3 , (NH4) 2 CO 3 , Sb2O3; BaCO3,
		BaSO4; Bi2O3, C (charcoal), CuO,
		Fe2O3, MgO, KCl, K2O, K2CO3,
		KNO3, K2SO4, K2S, K2SO3, KCNS,
		SrCO3, SrSO4, S, TiO, ...

Table 3 : main materials (termed in related elemental quantities) involved in the Enschede fireworks accident [42]

 3

	materials/elements	quantities
		(kg)
	Carbon based (as C)	1150000
	Pb	22000
	Cu	13000
	Zn	21000
	Ba	2200

Table 4

 4 summarizes part of the analytical results from the study that focus on those species that, at some time during the accidental scenario, were measured in quantities exceeding what is referred to as admissible long term threshold values in the report.

Table 4 : concentrations of toxic species emitted during the Enschede accident (after table 5.1 in ref. [42])

 4

	Toxic	Concentrations vs phase (1, 2 or	long term
	species	3)	of accident (|i.g/m3)	value
		1	2	3
	PM 10	135	1045	290	40
	Cu	3.6	2.6	-	0.9
	(Mn)			(2.2)	0.6
	Ba	6.5	-	2.1	1
	Pb	1.5	23.1	2.8	0.5
	Cd	-	0.7	-	0.3
	Cr		0.07		0.0025
					(a)

(a) : admissible long term value refers to Cr 6+

Table 5 :

 5

	composition (mass %) of test smoke
		powders
	components	SP1	SP2
	lactose	30%	22.5%
	starch	30%	22.5%
	KNO 3	40%	45%
	(Notice : 'SP' stands for smoke powder)

Table 6 :

 6 combustion characteristics and products released from burning Smoke Powders in the Tewarson apparatus

			Combustion products	SP1	SP2
						40% KNO 3	45% KNO3
						Combustion rate (g/m 2 /s)
						140	400
						Emission yields (mg/g)
			CO 2			690.2	700.4
			CO			98.2	56.4
			Total hydrocarbons	16.2	6.8
			NOx			5.5	4.2
			Soot			19.5	18.2
			Ammonia		10.8	4.6
			Methylamine		<0.04	ND
			Dimethylamine		D	D
			Trimethylamine		D	D
			Formaldehyde		0.380	0.283
			Acetaldehyde		1.299	0.318
			Acrolein		ND	ND
			Pentanal		D	0.003
			Butanal		0.016	0.004
	5.2 Experimental	conditions	for	DSC
	experiments	on	Smoke	Powders	and
	corresponding results

Table 7 : conventional fires versus burning pyrotechnics: a comparison of governing paramaters affecting toxicity

 7

	parameters	conventional fires				burning pyrotechnics
	chemistry of	Building fires : CH-, CHO-, CHON-based C (charcoal), C x H y , C x H y O z , metallic
	combustible	natural or synthetic polymers (+small amounts of powders, S, P, other organic materials
	materials	Cl, S..)					(saw dust, wax..)
		Industrial fires : largely more variable in terms of
		chemical structures and chemical elements
		involved
	oxidizing stream air					solid oxidizers intimately mixed in
							pyrotechnics	compositions	(nitrates,
							chlorates,	perchlorates,	mainly
							inorganic.)
	mode of burning diffusive burning in air				decomposition / 'combustion' in kind of
							deflagration mode (at least one order of
							magnitude higher in speed)
	main toxic	CO, HCN, depleted O 2				metallic compounds (oxides or salts) with
	products	SO 2 ,HCl					mercury, lead, arsenic...?
	identified	Other	irritants	(acroleine,	aldehydes,	irritants or products of specific toxicity
	(acute/sub-acute)	isocyanates...)				(aldehydes...)	with low temperature
							systems
							needs further evaluation to balance
							current positions
	role of air	of prime significance: availability of air governs	limited role (in most cases) to:
		type of fire:
		-either fuel-rich (well ventilated)
		-or full lean (under-ventilated) [57]
	importance of	limited for the acute toxicity problem. Under 10
	aerosols/particles	|j.m, may however serve as carriers of adsorbed
		species inside the respiratory tract
	Geometry of	Materials when burning can generally be
	sources	assumed as fixed 'sources terms' of pollutant or
		toxic species
	pertinent lab-	So-called fire physical models with bioassay
	scale tools	coupling	capacities	and	lab-scale	fire
		calorimeters (such as the FPA)
		Well identified in literature and standards (see in
		particular ISO DTR 16312-2 (2006) [46]


T Araodeo

M Audelet

M Attoui

O Le Ihan

£ Fre Afon

Nanoparticle manufacture ambient air chemical and ph sical sur e as a tool for accidentai and chronic risk assessment

Nowadays, nanotechnology lets foresee many opportunities and benefits for new materials with signifîcantly improved properties as well as revolutionary applications in large industrial flelds. Analysts hâve estimated that thé size of thé market was 900 million Euro in 2005 and will be 11 billion Euro in 2010.

However, nanomaterial industrial stakeholders are currently encountering potential problems with hazard control in their production plants. Release of nanoparticles in air can lead to violent chemical reactions and even explosions because of their small size and energetic properties, and hence high chemical reactivity.

Another major safery concern is thé impact of manufacturing nanoparticles on thé environment and more specifically on thé health of workers and of neighbouring populations. Thus, a key issue consists of controlling thé release of nanoparticles with chemical or physical toxicological impacts under thé ambient background.

The methodology proposed hère is based on ambient chemical and physical on-line characterisation. The LIBS technique has been proposed as an analytical technique for both on-line émission monitoring and workplace survey. As we also need on-line information on thé particle size distribution, thé DMA technique, which is based on electric mobility classification, has been combined to LIBS technique as shown by previous results on thé 000).

The purpose of this work is then to optimise such a combination in order to reach ambient air characterisation of manufactured nanoparticles below 100 nm size.

Laboratory studies and optimisations are carried out in order to optimise thé performance taking into account spécifie constraints for thé development of a field instrument. As a conséquence, increasing S R gain (ratio of thé peak émission intensiry over thé average continuum émission) and therefore détection limit under a hélium atmosphère (Mukher ee and al, 005) can not be applied in our case, as we hâve to deal with ambient air condition.

At a first stage, to valid thé LIBS technique as a tool for chemical identification in ambient air, feasibility studies hâve been carried out on organic and non-organic trace élément identification in bacteria (E. colî). The performance of thé LIBS technique has been evaluated for several laser wavelengths (266, 532 and 1064 nm) and puise durations (nanosecond and femtosecond) (Baudelet and al,005). Our results show in particular thé advantage related to thé use of UV radiation (266 nm) for thé détection of thé metallic trace éléments. The metallic élément détection performance of thé nanosecond UV laser is shown to be comparable to that of thé ultra-short femtosecond laser, and to be much higher than that of nanosecond IR (or visible) laser as shown in thé figure 1. In order to evaluate thé feasibility of ambient air characterisation, a sait détection in ambient air using nanosecond IR laser puises was carried out. A détection limit of 7 g m 3 with a S R of 1.2 was obtained for a size distribution centred at 50 nm. This performance fits well thé criterion of risk assessment where a value smaller than 1 mg m 3 is required.

4000(jg*rû 7|jg*n3 56pgW3

Wrvelengtli (nm) Figure. 2: LIBS détection of sait (thé doublet of thé Na) nanoparticles concentration in ambient air., The size distribution is centred around 50 nm for dry NaCl particles.

Based on thèse results, modifications on thé optical setup are tested and laser studies are performed in order to decrease by a factor of thousand thé détection limit of such preliminary results. In partiçular, S R gain studies hâve been performed using UV and IR nanosecond puises but also evaluated thé S R ration increase using femtosecond puises. Tests currently performed were made on both nanoparticles of sait and métal in air matrix should permit to reach détection limit in ng m 3 range and thus in accordance with chronic risk assessment. Finally, we are performing new plasma laser génération to increase thé S R gain by combining UV and IR nanosecond lasers in a dual puise configuration. breakdown spectroscopy", to be published in Appl. Phys. Lett. ( anuary 2006)

Figure 1 :

 1 Figure 1 : Comparison between potassium line émissions from bacteria (E colî) excited by nanosecond UV or IR radiations at thé same energy per puise (thé intensities of thé K lines are normalized by thé line intensiry of thé carbon 247.9 line).

  .

						D.W. Hahn, and M.M.Lunden, "Détection
						and analysis of aérosol particles by laser induced
						breackdown spectroscopy", Aérosol Sci. Tehnol
						(2000)
						D.Mukherjee,	A.Rai,	M.R.	achriah,
						uantitative laser breackdown spectroscopy for
						aérosols via internai calibration: Application to thé
						oxidative coating of aluminium nanoparticles ,
						ournal of aérosol science, 2005
						This work was supported by thé FP6 European
						Integrated Project NANOSAFE2, thé French
						Ministry of Environment and thé General Council
						of Picardie in France.
	CONCLUSIONS
	It has been demonstrated thé feasibility of an
	ambient	air	on-line	characterisation	of
	manufactured nanoparticles combining physical
	characterisation using dedicated DMA technique
	and chemical identification with field optimised
	LBBS technique. Results obtained on demonstrator
	based instrument should show détection limit
	around ngm 3 in UV-IR dual nanosecond puise
	régime.
	Keywords:	Nanoparticle,	plasma,	chemical
	analyses, size distribution, number concentration,
	on Une