(1) You must make sure mechanical ventilation meets the requirements of one or more of the following standards:

(a) NFPA 34-1995, Standard for Dipping and Coating Processes Using Flammable or Combustible Liquids;

(b) ACGIH's "Industrial Ventilation: A Manual of Recommended Practice" (22nd ed., 1995);

(c) ANSI Z9.1-1971, Practices for Ventilation and Operation of Open-Surface Tanks and ANSI Z9.2-1979, Fundamentals Governing the Design and Operation of Local Exhaust Systems.

Note:

Some, or all, of the consensus standards (such as ANSI and NFPA) may have been revised. If you comply with a later version of a consensus standard, you will be considered to have complied with any previous version of the same consensus standard.

(2) You must limit the vapor area to the smallest practical space by using mechanical ventilation.

(3) You must keep airborne concentration of any substance below twenty-five percent of its lower flammable limit (LFL).

(4) You must make sure mechanical ventilation draws the flow of air into a hood or exhaust duct.

(5) You must have a separate exhaust system for each dip tank if the combination of substances being removed could cause a:

(a) Fire;

(b) Explosion; or

Reference: You need to keep employee exposure within safe levels when the liquid in a dip tank creates an exposure hazard. See Airborne contaminants, WAC 296-841-099 through 296-841-20025.

Note:

You may use a tank cover or material that floats on the surface of the liquid to replace or assist ventilation. The method or combination of methods you choose has to maintain the airborne concentration of the hazardous material and the employee's exposure within safe limits.

PDFWAC 296-835-11010

Provide proper ventilation for the vapor area.