Exhaust motors, fume hoods

A fume hood is constructed in the manner shown in figure 6. Strike drew the frame as being made of lumber but it can be made of rebar or, preferably, from PVC pipes and joints so that it can be assembled and disassembled with ease. The frame is enclosed with plastic drop cloths or any semiclear plastic sheeting. The front face of the hood is halfway covered with plastic while the bottom half is exposed to allow one to move objects in or out and to manipulate things. On top of the chamber is attached some clothes dryer duct or some such crap which is led to a leaf blower or blower motor. The exhaust from the blower is led away to the outside. 

The placement of fume hood exhaust motors is an important fire protection consideration. Fume hood exhaust motors should be placed on the roof of the building or in a fire secured penthouse. 

Placement of the exhaust motor directly on top of the fume hood is a fire and explosion hazard as, except for specially order motors, these motors are not sealed and are thus exposed to the chemicals they are exhausting. 

If a special-flammable storage cabinet ventilation system is installed, it should employ an AMCA-C type spark-resistant fan and an explosion-proof motor. Most fractional horsepower fans commonly used for this purpose do not meet this criterion and should not be used. If the building has a common fume hood exhaust system, then it is appropriate to hook a flammable-storage cabinet up to it if it must be ventilated. 

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