API RP 505 (hazardous area classification) Annex D

[Guidoo]

API RP 505 for "Classification of Locations for Electrical Installations at Petroleum Facilities Classified as Class 1, Zone 0, Zone 1, and Zone 2" contains an Appendix D (Informative Annex) with an alternate method for area classification.

Radii as found using this alternate method can be quite different from the ones calculated using methods from chapters 8-10 of the Recommended Practice. Anyone having any idea why this appendix is there, an when it should be applied?

 

[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... :-/