Figure 5-2。  Workbench hood。

Figure 5-3。  Floor exhaust。

NOTE: Mount the work piece on a mechanism for easy rotation。 This will reduce the dead air space that occurs when working on raydomes, boat hulls, and other large objects。

Figure 5-4。  Spray up booth。

Figure 5-5。  Ventilated sink。

5-4。2。4 Spray Up Booths。  Design a spray up booth as shown on Figure 5-4。 Use the spray up hood design in shops where spray up and lay up are performed in the same booth。 Separate operations in this booth from any cutting, grinding, and sawing operations when conventional hand tools are used。

5-4。2。5 Ventilated Workbench and Sink。  Design a ventilated workbench as shown in Figure 5-2 for small work pieces。 Use a similar workbench for resin preparation and mixing as shown on Figure 5-5。 Eliminate the drawers and increase the size of the hood face by extending it to the floor if 55-gallon drums are used during resin preparation。 Use aqueous emulsion cleaners to reduce styrene and acetone exposure。

5-4。3 Ductwork。  Design a 17。8 m/s (3,500 fpm) minimum transport velocity for LVHV hand tools, and grinding and spray up operations to prevent particulate material from collecting in the ductwork。

a。 Size the ductwork carrying vapor generated during lay up and mixing operations for a minimum transport velocity of 12。7 m/s (2,500 fpm)。  Use sheet metal as duct material since it is non-combustible。 Route the ductwork directly to fans located outdoors。  See paragraph 2-4。1 for further information on ductwork。

b。 Consult with a fire protection engineer and use UFC 3-600-01 to design a fire protection system for the ductwork when required。 Condensation of flammable vapors, i。e。 styrene and acetone, may occur and pool in the ductwork as it passes through an area with a lower temperature。

5-4。4 Fans。  See paragraph 2-4。2 for general considerations。

5-4。5 Weather Stack Design and Location。  See paragraph 2-4。3 for exhaust stack design guidance。

5-4。6 Air Cleaning Devices。 Use separate air cleaning devices for grinding, buffing and polishing operations where particulate material is generated。 Use separate air cleaning devices for lay up and mixing operations where flammable vapors are generated。 Consult the air pollution control authorities for details on local requirement。

5-4。6。1 Grinding Operations and Hand Tools。  Use a fabric collector for grinding operations and LVHV hand tools。 Consider using a disposal chute with a motor-driven rotary air lock in shops with a large particulate volume。

5-4。6。2 Spray Up Operations。  Spray-up operations release a combined contaminant of wet resin laden fiber and organic vapors。 Therefore, separate spray up operations from all other operations。 Install an air-cleaning device for vapors。 Install layered prefilters on the spray up hood face instead of the perforated plate to prevent wet airborne resin from hardening in the ductwork and collectors。 Peel off and discard a layer of the prefilter when its surface becomes loaded as indicated by the hood static pressure gauge。  This continues until only the base filters remain。  After that, replace the

entire prefilter section。 Specify a filter material that is not damaged by the styrene and acetone vapor produced in FRP facilities。

5-4。7 Industrial Vacuum System。  Install a vacuum system; see Figure 5-6, to exhaust fibers, dry resin and dust from LVHV hand tools when they are used。 The vacuum system also allows workers to conduct shop cleanup and to decontaminate their protective outerwear。 ACGIH IV Manual, Chapter 10, gives design details and illustrates power tools using LVHV vacuum systems。 The large size and high terminal velocity of the particulates produced by the hand tools requires a high velocity vacuum take-off hood for each tool。 Generally, design the takeoff hood into the tool's safety guard。