From: ACTSNYC**At_Symbol_Here**CS.COM
Subject: Re: [DCHAS-L] Overspray from screen print cleaning
Date: January 28, 2012 2:15:11 PM EST
Reply-To: DCHAS-L <DCHAS-L**At_Symbol_Here**MED.CORNELL.EDU>
Message-ID: <38043.7e244e88.3c55a33f**At_Symbol_Here**>

Debbie, I'm counting on you to send my other response to you on this issue to Don.


1.  To assume that the spray is a nuisance mist, you would have to assume that untested chemicals in classes in which other members have been found to cause cancer and other toxic effects are somehow "safe."  The precautionary principle should be used here and untested chemicals should not be assumed to be without hazards.

And these aren't workers that are exposed.  They are a high risk population: kids who may have asthma, have one or more disabilities, may be pregnant, and so on.  Vent it as best you can.

2.  The resistance added to any recirculating HVAC ventilation system by introducing a filter on the air intake is going to stop it almost dead.  The motors will keep running but the fans will not draw significant air at even slightly elevated static pressure.

Instead, leave the return air grilles alone and reroute the system to the outside for 100% exhaust.   It should all be replaced by round duct, but if it has to stay square it will still work for a while.  Use a backward inclined centrifugal fan to power it which cleans itself and prepare to replace the ducts in 20+ years since they are probably lined and won't clean well.

It's expensive and costs a lot of energy, but your printmaking, painting, ceramics, sculpture, jewelry, and every class that involves chemicals should be exhausted to the outside.  If you can't do this, talk to the faculty about changing materials.  There are processes and materials in printmaking and painting that don't require special ventilation.  And they can still have a good program that can be certified by NASAD.


In a message dated 1/28/2012 1:13:50 PM Eastern Standard Time, dabramow**At_Symbol_Here**BRYNMAWR.EDU writes:

Assuming the overspray is simply a nuisance and local exhaust is truly unnecessary, perhaps you could place particulate filters over the return air intakes.  This could be as crude as taping air handler, furnace, or paint booth overspray filters over the openings, or having metal filter holders installed over the intake to make filter changes easy.  Could even add magnehelic guages to monitor the differential pressure to know when it's time to change the filters.   This should keep the material out of the system, as long as there are no volatiles involved that would be a concern if they passed through or  evaporated off the filters and were drawn into the system.


Donald Abramowitz, CIH
Environmental Health &Safety Officer
Bryn Mawr College
Bryn Mawr, PA

Please excuse the cross-postings - I need to cast a wide net.


Our Design department has moved into new digs in a renovated older building (early 1960's vintage).  It has a return air system with openable windows.


In the screen printing shop, they treat the screens with an emulsion and various inks to form the image.  After they develop the image and use the screen, the dried ink and emulsion need to be removed from the screen.  They use a stripper and power washer to clean the screens.  The cleaning process occurs in the shop in a large, stainless steel sink, installed against one wall in the shop.  The sink is fitted with a solids trap.  All of the emulsions, inks and strippers are water-based, don't have any hazardous materials in them and are allowed to go down the drain.


But the cleaning process puts water spray and particulate into the air - in a return air building - and my shop manager is concerned about occupant exposure and contamination of the supply air from the overspray.  Adding exhaust ventilation isn't possible, for a variety of reasons.  Cleaning the screens outside isn't possible either, as there are strict storm drain rules in California.  There haven't been any complaints yet but they just moved into the space last quarter.


Any ideas?  I'm fresh out.






Debbie M. Decker, Campus Chemical Safety Officer
Environmental Health and Safety
University of California, Davis
1 Shields Ave.
Davis, CA  95616
(530)754-7964/(530)681-1799 (cell)

(530)752-4527 (FAX)
Co-Conspirator to Make the World A
Better Place -- Visit and join the conspiracy

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