Health and safety risk assessment methodology to calculate reverse airflow tolerance in a biosafety level 3 (BSL-3) or airborne infection isolation room (AII) environment

Abstract

A novel methodology is proposed to calculate how much air displacement and contaminant leakage might occur during a power outage that may result in a momentary positive pressure reversal in a BSL-3 facility. Note that the ultimate goal in design and operation of a BSL-3 facility is to achieve sustained directional airflow such that under failure conditions the airflow will not be reversed. The proposed methodology should be applied when and only when all other measures to achieve zero tolerance have been ruled out. Only after determining that zero tolerance cannot be achieved for the BSL-3 facility in question should the model be employed to perform a health and safety risk assessment to determine the reverse airflow tolerance. The methodology is applicable to other room types, such as airborne infection isolation rooms, that use sustained differential air pressure as one means to prevent particle migration across a boundary.