have been no instances recorded where the toxicity of these solvents affected the 

 operator, it is believed that this condition could develop were the fumes sufficiently 

 concentrated. Maximum safe concentrations of these toxic materials are as 

 follows: 



Parts per million 



Methyl mthea,r 



1Z J ' 200 



Ketone 



Ethyl 500 



. : 400 



Acetone 



500 



Wherever the possibility of excessive density occurs, exhaust fans should be used 



It is highly important that all precautions listed under the heading of Safety be 



followed in the application of plastic sealing. 



Figure 3. — Pigmented plastic coating in pressure pot. Note.: Several unsafe prac- 

 tices are shown. Open pressure pot should be kept away from gasoline-operated 

 compressor. Spilled material indicates the importance of performing operation 

 elsewhere, and being careful to prevent spilling. 



An especially desirable feature is the toughness and resistance of plastic film 

 to injury. Although tensile strength is not essential, it makes this product more 

 durable and less subject to abrasions when bumped or scraped by the movement 

 of hogsheads. Sharp instruments or nails puncture it easily and for this reason 

 plastic should not be used in sealing the floor of a building unless the work can 

 be done from the lower side. 



Plastic coating, when applied without the use of a binding agent, is readily 

 strippable or removable. When a binding agent is applied first, the plastic will 

 then be more or less permanendy bound to the surface to be sealed. This type 

 of application adheres satisfactorily to all kinds of building materials, including 

 concrete, steel, wood, brick, and hollow tile. 



