Hi Ralph,

I've run into a "similar" situation before.

We used what is called an "air proving switch", which is basically a pressure sensor with an actuator that is in the form of an aluminum paddle situated within the airstream at the preferred point of measurement. When there is enough pressure, the paddle moves.

The switch was tied to a visual indicator.

The procedure was to turn on the fan and wait until the light came on (enough air flow/pressure at the source to move the paddle) before work could commence.

If you wield the power of the interweb, and search for "air proving switch", you will get many examples of switches and manufacturers that provide them. There are many different switches for different applications with different sensitivities. Your fume hood installer/HVAC contractor may have a few suggestions.

Regards,

Neil Patterson
General Manager

Photech Environmental Solutions Inc.
940 Chippawa Creek Road
Niagara Falls, Ontario, L2E 6S5
Canada

Office: 905.938.9465
Phone: 877.938.9465
Fax: 877.938.8978
Web: www.photech.com
E-Mail: npatterson**At_Symbol_Here**photech.com

-----Original Message-----
From: ACS Division of Chemical Health and Safety [mailto:DCHAS-L**At_Symbol_Here**PRINCETON.EDU] On Behalf Of Stuart, Ralph
Sent: November-09-16 3:57 PM
To: DCHAS-L**At_Symbol_Here**PRINCETON.EDU
Subject: [DCHAS-L] Exhaust fan design question

I have a exhaust fan design question that someone in this group may be able to comment on. We have a spray paint booth in our wood shop (2014-vintage) with a lab style fan (Vektor-H Laboratory Exhaust System - Greenheck Fan) on it. It is turned on and off as needed with a off/low/high switch, but when we turn it on, there is no apparent response for about 5 minutes. This makes it difficult to convince the booth users that the system is working, since they may complete their work in the booth (e.g. spray painting a piece) before the system is fully operational.

I realize that most lab fan systems are on 24/7, but I wonder if anyone has run into similar situations with systems which are designed to be turned on and off routinely?

Thanks for any thoughts about this.

- Ralph

Ralph Stuart, CIH, CCHO
Chemical Hygiene Officer
Keene State College

ralph.stuart**At_Symbol_Here**keene.edu

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For more information about the list, contact the Divisional secretary at secretary**At_Symbol_Here**dchas.org

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This e-mail is from DCHAS-L, the e-mail list of the ACS Division of Chemical Health and Safety.
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