Q&A | ANSI/IIAR 2-2021 Natural Ventilation Requirements


Question: Does my machinery room need an emergency ventilation system if it only has three walls?

Answer: It may not require mechanical ventilation and could meet the requirements for “Natural Ventilation”.


ANSI/IIAR 2-2021 §7.3.2 states that for outdoor systems, natural ventilation can be utilized instead of mechanical ventilation. For a machinery room to qualify for natural ventilation, the open area (in square feet) must be larger than the square root of the system inventory (in pounds). 



A machinery room has a large opening in the wall that measures 10 ft wide x 10 ft high. The system is small, containing only 5,000 lbs of ammonia. 


In this example, the natural ventilation requirement has been met and the machinery room does not require mechanical ventilation according to ANSI/IIAR 2-2021.

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