Paints surface contaminants

Airborne contaminant movement in the building depends upon the type of heat and contaminant sources, which can be classified as (1) buoyant (e.g., heat) sources, (2) nonbuoyant (diffusion) sources, and (d) dynamic sources.- With the first type of sources, contaminants move in the space primarily due to the heat energy as buoyant plumes over the heated surfaces. The second type of sources is characterized by cimtaminant diffusion in the room in all directions due to the concentration gradient in all directions (e.g., in the case of emission from painted surfaces). The emission rare in this case is significantly affected by the intensity of the ambient air turbulence and air velocity, dhe third type of sources is characterized by contaminant movement in the space with an air jet (e.g., linear jet over the tank with a push-pull ventilation), or particle flow (e.g., from a grinding wheel). In some cases, the above factors influencing contaminant distribution in the room are combined. 

In general, there are two types of surface contamination (1) organic contamination—such as oils, greases, paint coatings etc. and (2) inorganic contamination —such as rust, oxide films, corrosion products, scale, anodic films etc. Although these two types of contaminant can be removed simultaneously, it is simpler to consider the cases separately. 

A munition loses this surface contamination within days or weeks after being placed. This time depends on many factors, but it is clear that there may be an initially higher level of molecules entering the local environment from a recently placed, or fresh munition. This is a transient effect that normally gives way to a more steady-state supply of molecules. In munitions that have painted surfaces,... 

Surface contamination was found to vary widely from mine to mine, but effective average contamination from a number of mines of several national origins seems to be about 15 to 18 ng/cm2. Contamination in the painted surface of mortar and artillery shells was similar [8],... 

The prior use of kerosene or other solvents in PCB spill cleanup activities may interact with the substrate and increase the migration of PCBs into the contaminated media making removal more difficult. Painted surfaces should be patch tested prior to application as paint softening or discoloration may occur. 

The potential fire hazard presented by waste tire stockpiles has been realized a number of times in the past decade. Several stockpiles have burned until their tire supplies were exhausted which, depending on weather conditions, may be a few days to more than a year. Air pollutants from tire fires include dense black smoke which impairs visibility and soils painted surfaces. Toxic gas emissions include polyaromatic hydrocarbons (PAHs), CO, S02, NOj, and HC1. Following tire pile fires, oils, soot, and other materials are left on site. These tire fire by-products, besides being unsightly, may cause contamination to surface and subsurface water as... 

Problems of adhesion can arise with most substances that are painted—not only plastics—especially if the surfaces to which paint is applied are not clean. Hence, for the best results, the plastic articles always should be free from loose particles and from other surface contamination (such as moisture, or oils). However, the plastics that are difficult to paint exhibit also one or both of the following characteristics. 

For the first two series of experiments, the coupon was submerged completely in one of the two test contaminants, patted lightly with a lint-free tissue to remove excess material, and weighed. Loading was controlled to 0.005 g from run to run to minimize effects of surface concentration differences. In later series, dopants were applied to one side of the coupon which was marked to designate an area so that the contaminated area would remain constant from run to run. The contaminants were applied to this area with a small, short-bristled paint brush. Contaminant mass for each of these series was kept constant from run to run to within 0.0001 g. 

Small Areas Ventilation. In heavily contaminated areas, decontamination with copious amounts of aqueous sodium hydroxide solution (a nunimum of 10 percent by weight) may be required. If sodium hydroxide solution is not available, then sodium carbonate may be used. Removal of porous material, including painted surfaces, that may have absorbed Nerve Agent vapor may be required as these materials could continue to re-release vapor after exposure has ceased. 

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