Too many safety personnel are not sufficiently familiar with the critical role Vapor Pressure (VP) plays in managing hazardous materials. From our PPE Hazard Assessments, Respiratory Protection, to how we respond to these hazardous materials when there is a LOPC event involving them. But VP also plays a major role in how we DESIGN our workplace that stores/handles/processes hazardous materials. For example:
In an earlier post, we discussed the challenges of having 19% Aqua Ammonia on site in quantities that exceed its MAQ of 20 pounds. The MAQ is 20 pounds because the Fire Code requires that any toxic liquid with a VP > 1 PSIA (52 mm Hg) be managed as a “highly toxic liquid”. This is KEY in understanding the DESIGN of the areas where these hazardous materials are stored/handled/processed. The MAQ went from 100 pounds to 20 pounds based SOLELY on the VP of the Hazardous Material!
VP of 19% Aqua Ammonia @ 77F is 264 mm Hg or about 5.1 psia
1 PSIA = 52 mm Hg
e. The maximum allowable quantity per control area for toxic liquids with vapor pressures in excess of 1 psia at 77°F shall be the maximum allowable quantity per control area listed for highly toxic liquids.