Low VOC Environmental Room

[BronYrAur]

I am tasked to design an HVAC system to keep low VOC levels in an environmental room. The room was formerly a clean room but now it is vacant. It is approximately 1000 sqft with one wall exposed to outside (500 sqft). There is a layin ceiling with a space above before reaching the roof. The remaining sides are exposed to unconditioned plant spaces. Internal loads will be minimal - lighting and no more than 3 people.

Particulate is not a concern, but VOC levels are. VOC levels cannot exceed 5 micrograms per cubic meter for any individual compound, including formaldehyde, and the total VOC level cannot exceed 25 micrograms per cubic meter.

temp needs to be 73 deg +/- 3 deg and humidity 50% +/- 10%

Room will have painted steel walls and probably the same for ceiling tiles.

Any suggestions on HVAC equipment to handle this room?

 

[ChasBean1]

What's existing? If existing HVAC was capable of satisfying clean room requirements it would probably be more than sufficient for your application.

If you need a new AHU, you'd probably do fine with 1,000 cfm and a good positive pressure, maybe returning 700 cfm. A VOC free air intake would be away from roofing tar and exhausts and the AHU might be equipped with carbon filtration.

(One note - if the wall exposure is on the sunny side, you might go with 1,500 cfm supply and 1,200 return. You should probably do a load calc. as it could vary quite a bit w/glazing, etc.)

If you have new paint, caulk, etc. you might also consider a good, high temperature bake-out period followed by TVOC sampling prior to use.

 

[BronYrAur]

I have no HVAC system now. The clean room equipment is long gone.

 

[DrRTU]

Your problem is a control issue. Obtain a list of each VOC compound the client needs to monitor and make the list part of your contract. You could have hundreds of compounds to monitor. The common "HVAC" VOC sensors look at a peak ppm level. Separate "tuned" sensors and ongoing calibrations can be costly. Verify the design assumption of your OA does not contain VOCs from local emissions such as the roof or process exhausts. Check all the existing building materials. We did a law office in which the client blamed the existing / modified vent system for unusual odors. They focused on duct liner & mastic. It was an existing sheet good flooring off gassing. At your low levels, off gassing will drive the system to 100% OA. Operate the fan continuous (24hrs), select an AHU without internal insulation (external cover), check the sealer in the AHU for VOCs, clean the duct before installation to remove mill / forming oils and commission the system similar to a LEED building. Charcoal filters will not capture all compounds. The commission will prove up the design.