How well do you know ventilation requirements in the workplace?: Answers

Scenario 1: Yes.  Welding ventilation techniques vary. Often, however, a relatively simple ventilation method like the appropriate use of fans is all that is needed. OSHA’s standard at 1910.252(c) specifies that if mechanical ventilation is used, it must consist of either:

• General mechanical ventilation, or
• A local exhaust system.

Mechanical ventilation changes the air. In contrast, local exhaust systems, like hoods at the arc and fans, remove fumes and smoke at the source. Both ventilation methods help to reduce the concentration of hazardous fumes and gases.

Scenario 2: No. When mechanical ventilation is used in dipping and coating processes, each dip tank must have an independent exhaust system unless the combination of substances being removed will not cause a fire, explosion, or chemical reaction. Mechanical ventilation must draw the flow of air into a hood or exhaust duct. Exhaust air may not be recirculated when any substance in that air poses a health hazard to employees or exceeds 25 percent of its lower flammable limit (LFL).