Screening smokes effectiveness

A third screening smoke-type is white phosphoms [7723-14-0] (WP), P (see Phosphorus and THE phosphides), which reacts spontaneously with air and water vapor to produce a dense cloud of phosphoms pentoxide [1314-56-3]. An effective screen is obtained as the P2O5 hydrolyzes to form droplets of dilute phosphoric acid aerosol. WP produces smoke in great quantity, but it has certain disadvantages. Because WP has such a high heat of combustion, the smoke it produces from bulk-filled munitions has a tendency to rise in pillarlike mass. This behavior too often nullifies the screening effect, particularly in stiU air. Also, WP is very brittle, and the exploding munitions in which it is used break it into very small particles that bum rapidly. 

Chemical. Used for riot control, incendiary, smoke screening, smoke signalling incapacitating purposes Offensive. Used for their blast effect Practice 6 Training. Used for training personnel in use, care handling of service grenades... 

Chemical Sprays Liquid sprays from aerial release devices designed to cause harassing or casualty effects(war gases), screening (smoke compns), or fire.s(incendiarycompns)... 

Brown BJ, Affleck GE, Cummings EG, et al. 1981. The subchronic effects of repeated exposure to white phosphoms/felt screening smoke in rats. Report No. ARCSL-TR-80068, AD-B05848L. 

Uses Powerful incendiary burning pieces adhere to skin and clothes and have a limited casualty effect. Was largely used by Allies in World War 1 for screening smokes in hand grenades and mortars. It is now also extensively used for incendiary purposes, in shells, bombs, and incendiary leaves, P5. 

Uses For producing screening smokes (British attack on Zeebrugge). In combination with ammonia vapor it forms smokes which resemble natural fog and which are effective for camouflaging troop or ship movements. The smoke is generated from a smoke funnel. One cylinder contains liquid ammonia the other cylinder is charged with silicon tetrachloride containing about 10 per cent carbon dioxide under a maximum pressnre of 550 lb/sq. in. at 55°. 

The effectiveness of screening smokes depends on obscuration by particles that reflect, refract, and scatter light rays. The effectiveness of a smoke increases with its atmospheric concentration, as shown in Table 18.1. 

The unprotected user or bystander could have skin contact with screening smokes, and depending on the nature, physical properties, and chemistry of the smoke there may be a potential for local and systemic adverse effects. Thus, it is considered that the following studies should be conducted ... 

It is unlikely that there will be significant percutaneous toxicity under the usual conditions of exposure to screening smokes. However, if primary and cumulative skin irritation tests suggest that there may be systemic effects, then it will be appropriate to conduct more detailed monitored studies for percutaneous toxicity. 

Small-Scale Clinical Trials. Such trials involve exposure of individuals to the active substance or dissemination formulation with clinical monitoring for the specific organ, tissue, or system of concern with respect to potential adverse effects. For example, quantifiable exposure to a screening smoke with monitoring for respiratory function tests. 

Screening smokes, by their intended use, are deliberately released into the environment, albeit in localized and very small amounts. Thus, the possibility for environmental problems, including ecotoxicological issues, needs consideration. Particular aspects that may need to be taken into account include local decontamination, phytotoxicity, effects on domestic and wild animals, avian and aquatic toxicity, contamination of food and drinking water, effects on plant sewage organisms. 

Weimer, J.T., Affleck, G.E., Farrand, R.L, Lee, F.K., and Pellerin, R.J., The acute and chronic effects of repeated exposure to United Kingdom red phosphoms screening smokes in rats, mice, guinea pigs, and rabbits. Technical Report ARCSL-TR-79053, Chemical Systems Laboratory, US Amiy Armament, Munitions and Chemical Command, Aberdeen Proving Ground, Edgewood, MD, 1980. 

Where screening smoke must be delivered by explosive action, and where at the same time smoke screens without fire hazard are desired, a solution of 55 parts of sulfur trioxide (SO3) in 45 parts of chlorosulfonic acid (CLSOjH) is cheap and effective though its screening power is about one-half or less that of phosphorus. This FS mixture and the more expensive and otherwise less desirable titanium tetrachloride (TiCL4) called FM become aerosolized droplets only in the presence of water and presumably display their power of obscuration best and fastest in humid air. 

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