(1) The employer 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 the employer complies with a later version of a consensus standard, the employer will be considered to have complied with any previous version of the same consensus standard.

(2) The employer must limit the vapor area to the smallest practical space by using mechanical ventilation;

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

(4) The employer must make sure mechanical ventilation draws the flow of air into a hood or exhaust duct;

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

(a) Fire;

(b) Explosion;

Reference:

The employer needs to keep employee exposure within safe levels when the liquid in a dip tank creates an exposure hazard. See Respiratory hazards, chapter 296-307 WAC, Part Y-6.

Note:

The employer 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 selected by the employer has to maintain the airborne concentration of the hazardous material and the employee's exposure within safe limits.

PDFWAC 296-307-45010

Provide proper ventilation for the vapor area.