Chemical agents persistent

Table 2-5. Chemical Agent Persistency in Hours on CARC Painted Surfaces...

Table 1-4. Chemical agent persistency in hours on chemical agent resistant coated painted surfaces. ...

Schwebstoff, m, = Schwebestoff (Mil.) non-persistent chemical agent, -filter, n. filter for suspended material. 

An incapacitant is a chemical agent, which produces a temporary disabling condition that persists for hours to days after exposure to the agent has occurred (unlike that produced by riot control agents). Medical treatment while not essential may in some cases facilitate more rapid recovery. In the narrower sense the term has come to mean those agents that are ... 

Van Voris P, Cataldo DA, Ligotke MW, et al. 1987. Acute environmental toxicity and persistence of selected chemical agent simulants diisopropyl flourophosphate (DFP) and diisopropyl methylphosphonate (DIMP). NTIS No. AD-A181-309. 

It is a disease of cattle that is normally found in Africa. The natural reservoir is cattle. It is very resistant to physical and chemical agents. It can persist in necrotic... 

Vapor Density The ratio of the density of any gas or vapor to the density of air, under the same conditions of temperature and pressure that is, a measure of how heavy the vapor is in relation to the same volume of air. Air is considered to have a molecular weight of 1. As an example, the higher the vapor density is in relation to 1.0, the longer it will persist in low-lying areas such as valleys, trenches, and cellar holes. If the vapor pressure is less than 1, a chemical agent would will likely be non-persistent and dissipate quickly into the atmosphere. 

Persistent Agent Chemical agents that do not hydrolyze or volatilize readily, such as VX and HD. At the time of release, this agent can produce casualties for an extended period of time up to several days. Usually, it has a low evaporation rate. Since its vapor is heavier than air, its vapor cloud will hug the ground and accumulate in low areas. It is an inhalation hazard, but extreme care should be taken to avoid skin contact as well. 

The specter of chemical death persists. Like atom bombs, chemical weapons have been classified as weapons of mass destruction. But were they, and are they Nerve agents such as VX and sarin can certainly kill swiftly. But so can hundreds of familiar drugs and poisons. The real question is whether anyone within the limits of current technology can, in fact, use them effectively as lethal weapons on the battlefield. 

Once chemical agents are fully dispersed, they do not tend to persist in the environment because of their high chemical reactivity, particularly with water (hydrolysis). However, in extremely dry desert climates, they can persist for considerable periods of time (U.S. Army, 1988). The major environmental degradation products of nerve and mustard agents have recently been assessed and their persistence and toxicity evaluated. A potential hydrolysis product of VX (S-(2-diisopropylaminoethyl) methylphosphonothioic acid [EA-2192]) is a degradation product expected to display a high level of mammalian toxicity. Some mustard partial hydrolysis products are also toxic (Munro et al., 1999). 

The job of a chemical munition is to create a toxic environment over as much of the target as is compatible with the toxicity of its charge. It must convert its bulk load either into an even distribution of liquid or solid particles, or into a cloud of vapour, or into both. It must, additionally, do this in a certain time. These are strict demands, and they are made more severe by the diversity of chemical agents now in stockpiles. Each agent has a combination of physical characteristics and toxic behaviour that is unique but, nevertheless, all munitions work on the same basic principle they cause the transfer of energy from a store, generally an explosive, to the chemical load. The simplest chemicals to disperse are the volatile, non-persistent ones such as phosgene the hardest ones... 

Another reason one must consider the nature of the chemicals involved is that some chemicals pass through the body quickly, whereas others are stored in tissue. Exposure to chemicals which persist in tissue, such as Polychlorinated Biphenyls (PCB s) or DDT, of course, provides much greater opportunity for productive epidemiologic study than exposure to transient agents (such as trichloroethylene in Montgomery County). Many studies are undertaken long after active exposure has occurred. 

Permitted methods for off-site disposal of secondary waste vary from case-to-case, factoring in environmental considerations such as the potential environmental persistence of waste contaminants. Discussion of degradation rates for trace amounts of chemical agents under a variety of conditions are available in Waysbort et al. (2004), Bartelt-Hunt et al. (2006), and Columbus et al. (2006). Land disposal of hazardous waste is governed by Subtitle C of RCRA (40 CFR Parts 264/265). For landfill requirements, see 40 CFR Parts 264/265, Subpart N. 

Persistency is the length of time a chemical agent remains effective at the point of its release. If a gas remains in sufficient concentration to require protection of any kind at the end of 10 minutes, it Is classed as persistent. If the concentration at the end of 10 minutes is too weak to require any protection, the gas is classed as nonpersistenl. This is the American rule, but is not tho same in other countries, lit Home foreign countries three classes of pt rsisiency are rtxK>gniKed, as follows ... 

Persistence is, in general, an expression for the length of time during which a chemical agent remains and exerts its effect on the place where it has been released. The physical properties of a substance are nearly always the determining factors in its persistence. 

In considering persistence, we distinguish two groups of chemical agents ... 

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