An employee working in a room measuring 15 ft x 20 ft x 15 ft...

 

An employee working in a room measuring 15 ft x 20 ft x 15 ft sprays paint assembly parts using a paint containing hexane.

The PEL for hexane is 500 ppm. The employee wears a half-face, air-purifying respirator, but management would like to

install engineering control measures to reduce or eliminate the employee's exposure to hexane. The options are to:

(1) install a dilution ventilation system, or

(2) install a local exhaust ventilation system.

The employee works a 9-hour shift and has the following exposures:

For the general dilution ventilation system to work, there must be at least 20 room air changes per hour. The fan which

supplies air to this area produces 1,500 cubic feet per minute (cfm) (Q).

In order for the local exhaust ventilation system to remove the contaminant to acceptable concentrations, the capture

velocity must be at least 140 feet per minute (fpm). The proposed local exhaust system ventilation system uses a 1.0 feet

diameter duct and a fan that provides a total volume of 1,275 cubic feet per minute (cfm). The source of the contamination

is located 1.5 feet from the opening of the duct. Determine the appropriate ventilation control and calculate the capture

velocity. 

How do I calculate the dilution ventilation system based off the information provided above?