API RP 505 , ACH for Hazardous Areas 1

[yartes]

Based on API RP 505, the recommended ventilation for hazardous and non-hazardous areas is 12 and 6 ach respectively. From a Fugitive Emissions study I came up with only 2ach required for adequate ventilation. What flow rate I should apply? The recommended or the calculated?

Is that recommended ACH for the "whole room" or just the zone 1 area limited by the extensions suggested by API RP 505?

Please help... :-/

 

[Guidoo]

Did you actually read API RP 505? Especially sections 6.6 and Appendix B give quite clear guidelines on how to determine whether an enclosed area is adequately ventilated.

As per section 6.6.2.4.8, an enclosed location is adequately ventilated if a detailed calculation as per Appendix B shows that fugutive emissions concentrations remain below 25% of LFL. If calculated number of Air Changes per Hour is less than 3 it is recommended to provide continuous monitoring with fixed gas detectors.

I would say the whole room has to be adequately ventilated, since if this was not the case, the whole room would become zone 1...

 

[yartes]

Thanks Guidoo for your answer!

I have one simple question: If an enclosed-space is classified as Class 1, Zone 1, but the electrical equipment within this area is designed for Zone 1, Do I still need to ventilate at all??? ...or regardless of this I need to ventilate with the calculated flow from the fugitive emmissions study?

Thanks for your invaluable answer!

 

[Guidoo]

Yartes,

It is difficult to understand your question, but it seems like you mean this:

"If the enclosed area is classified as zone 1 based on the assumption that there is no adequate ventilation, do I still need to ventilate the enclosed area?"

The answer is no. You either have adequate ventilation or non-adequate ventilation. If you have non-adequate ventilation you can also have no ventilation at all (for area classification reasons). Note that there will normally always be some form of natural ventilation...