Indoor Air and Environmental Quality: Darkroom Ventilation

Darkroom Smoke Test

Question from the Mailbag:

How much ventilation is needed in a photographic darkroom?

Until 1999, Wisconsin had specific language in the Department of Commerce DCOMM 32.27 (formerly IHLR 32.27) on darkrooms.

32.27(9) DARKROOM VENTILATION. Exhaust ventilation shall be provided for all darkroom facilities. The capacity of the exhaust ventilation shall equal at least 12 air changes per hour, or an engineered local exhaust system shall be provided. History: cr. Register, March, 199l, No. 423, eff. 4-l-9l; am. (2) (b), cr. 2) (d), (e) and (9), Register, August, 1995, No. 476, eff. 9-l-95.

The 1998 revision to the Department of Commerce regulations removed the earlier language specific to darkroom ventilation, leaving only general Industrial Ventilation requirements for hazardous contaminants, under DCOMM 64.54(3).

DCOMM 64.54(3)Industrial Exhaust System

Industrial exhaust systems shall be installed and operated to remove harmful contaminants...

(b)Make-up air. Make-up air shall be provided as required by s. Comm 64.14. The quantity of make-up air shall equal at least 90% of air exhausted.

(c)Connections. connections between industrial exhaust systems that convey different materials, the combination of which may produce explosive, heat-generating, corrosive, toxic or otherwise dangerous mixtures, shall be prohibited.

In the UWM Mitchell Hall Darkroom Ventilation Upgrade (1998), an engineered local exhaust system was provided. With that in place, a system was installed that allowed for energy conservation after normal business hours. The system included an override capability which could be activated by workers who happened to come in after normal hours. The override was on a timer so the system would revert back to energy conservation after a certain time period.

To answer your question...12 air changes per hour is a good design specification. With 12 air changes per hour, the amount of air entering and leaving a darkroom should totally replace the air in the darkroom every five minutes.

We are open to ideas about energy savings during unoccupied periods.

Updated November 15, 2007