Volatile agents hazards from

Due to the volatile nature of most pulmonary agents, there is minimal extended risk except in an enclosed or confined space. Vapors have a density greater than air and tend to collect in low places. Solids that are dispersed as aerosols have little or no vapor pressure. Once the aerosols settle, there is minimal extended hazard from the agents unless the dust is resuspended. 

Contaminated patients pose a hazard to their attendants. Secondary contamination by contact with liquids or solids, e.g. powders, is an obvious risk, while off-gassing of volatile agents from clothing is, perhaps, less obvious. However, it was noted in the Tokyo subway incident (see Chapter 13) that hospital staff developed miosis as a result of exposure to sarin (GB) given off by patients clothing. The patients had themselves not been exposed to liquid sarin but only to sarin vapour and yet enough had been adsorbed... 

BSCs are designed to handle microbiological agents and are not designed to handle chemicals. It is possible to use small amounts of nonvolatile chemicals. You will see that some classes allow minimal amounts of volatile chemicals and this is only when they are ducted. The CDC/NIH BSC book calls these minimal amounts minute or small but it is not clear what these terms mean. However, the use of flammable or volatile chemicals in BSCs may present a very real hazard from fire or explosion if concentrations are not carefully controlled. Concentrations of flammable chemicals must never be allowed to approach the lower explosion limit. Procedures involving other than minute or small amounts of flammable or volatile chemicals should be carried out in a chemical hood, not a BSC. 

Vapour pressure This is defined as the partial pressure of the vapour in the atmosphere above a volatile liquid. Vapour pressure is temperature-dependent. The higher the temperature, the greater the vapour pressure. When vapour pressure reaches atmospheric pressure, boiling occurs. The importance of vapour pressure is that it gives an indication of the inhalational hazards from a toxic agent that is in a liquid state. Generally, a material with a low vapour pressure will not pose an inhalation hazard unless the patient is exposed to the material as an aerosol, in a confined space, for a prolonged period. 

Hazards arising from the oxidation of organic compounds are greater when the reactants are volatile, or present as a dust or an aerosol. Liquid oxygen and various concentrated acids, e.g. nitric, sulphuric or perchloric acid, and chromic acid are strong oxidizing agents. The use of perchloric acid or perchlorates has resulted in numerous explosions their use should be avoided when possible (refer to Table 6.5). 

Fire Hazard The volatile hydrides are flammable, some spontaneously so in air. All hydrides react violently on contact with powerful oxidizing agents. When heated or on contact with moisture or acids an exothermic reaction evolving hydrogen occurs. Often enough heat is evolved to cause ignition. Hydrides require special handling instructions which should be obtained from the manufacturers... 

The V-series of nerve agents are less volatile than the G-series but are better able to penetrate the skin. Although they are an inhalation hazard when they are in the air as vapor or aerosol, they are considered more of a percutaneous hazard. This series contains VX, VE, VG (Amiton), VM, VR (RVX, Russian VX), and VS. The V designation is considered to be derived from Victory, Venemous, or Viscous. 

Choking Agents are nonpersistent. Cold weather may decrease the rate of volatilization of any liquids present and increase persistency. Agents absorbed into porous powders may be significantly more persistent than normal. Decomposition products from the breakdown of some Choking Agents can pose a persistent hazard. 

Mustard is an oily liquid and is generally regarded as a persistent chemical agent because of its low volatility, usually allowing the liquid to remain on surfaces longer than 24 h. At higher temperatures, such as those in the Middle East during the hot season, 38°C-49°C (100°F-120°F), mustard vapor is a major hazard. The persistency of mustard (in sand) decreases from 100 to 7 h as the temperature rises from 10°C to 38°C (50°F-100°F) (CRDEC, 1990). 

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