HVAC for Nitric Passivation Line

[PolishedSteel]

Hi All,

I am foreign to HVAC but over a project to overhaul our production environment due to safety/quality slips.

The nitric passivation line is inside of a cleanroom (iso8). I plan to suggest walling off the passivation line from the surrounding cleanroom in order to help contain the area in the event of a nitric spill (which can occur periodically with NO2 ppm reaching 40.2 for a few minutes and taking quite a while to reduce to acceptable limits (10-60 mins). (STEL 5 ppm). Walling off to also reduce cost needed when it comes to reworking our HVAC

I am curious what governing doctrine should be referenced in regards to providing acceptable air quality. Current spec is to design to hit 10ACH in a volume of 6600 ft^3

We are looking to install returns near the floor to help pull particulate/ and fumes in and use laminar flow fan units with HEPA filtration in the drop ceiling to provide fresh air.

The Nitric storage tank fill have a hood over it to help exhaust anything when it is opened.

 

[SAK9]

I am not sure how partitioning up the passivation area will help if you have a common AHU serving both spaces and if it is based on air recirculation. Contamination will spread through to the whole space through the air distribution system in no time.

Secondly air change range recommended for a ISO Class 8 cleanroom is in the range of 15-20.Terminal HEPA is not a must. A central filter station in the AHU will suffice.