Ventilation System Tests


Machinery room ventilation systems have long been required by model codes and standards. Dating back to at least the 1967 Uniform Mechanical Code[1], refrigeration machinery rooms have been required to be configured with adequate ventilation in the event of a refrigerant release. While we have written previously about the current ventilation design, control, and testing requirements in ANSI/IIAR 2-2014, it is important to expand our consideration regarding the requirements for testing a machinery room ventilation system. To recap our previous blog post, as it relates to testing machinery room ventilation systems, ANSI/IIAR 2-2014 §6.14.8 requires that:

  • A schedule for testing the mechanical ventilation system shall be established based on manufacturers’ recommendations, unless modified based on documented experience. Testing shall include operation of the ventilation system based on ammonia detection at the concentration set forth in Section 6.13.2 and by a manual control switch required by Section 6.12.2.
  • Where manufacturers’ recommendations are not provided, the mechanical ventilation system shall be tested at least twice per year.

Notice the references above make no mention of testing the ventilation system airflow. In recent months we have witnessed CalOSHA cite several ammonia refrigeration facilities for failure to properly test their ventilation system. Interestingly, OSHA does not reference the PSM standard or ANSI/IIAR 2-2014 in their citation, but rather the lesser known regulation Title 8 CCR §5143General Requirements of Mechanical Ventilation Systems”. Specifically, this regulation requires that:

The ventilation rate of every mechanical ventilation system used to prevent harmful exposure shall be tested after initial installation, alterations, or maintenance, and at least annually, by means of a pitot traverse of the exhaust duct or equivalent measurements. Records of these tests shall be retained for at least five years.” [Title 8 CCR §5143(a)(5)]

For example, on 10/4/16, OSHA cited a California facility for failure to comply with the above-stated requirement. In the citation notes, OSHA indicated that “the employer did not test the ventilation rate of the mechanical ventilation systems used to prevent harmful exposure of ammonia in North and South machinery rooms. The employer did not provide test records as required.”

Airflow tests can be conducted using an anemometer to measure the velocity of air at the fan discharge. We recommend taking measurements at several locations and averaging the results. Once the air velocity has been determined, the airflow (CFM) can be calculated by multiplying the velocity by the fan discharge area.

Consideration can also be given to performing an additional test using a smoke candle to subjectively determine if make-up air is adequate and if the room is free from dead spots. These tests can expose ventilation system weakness and can be an effective training tool for employees that work inside a machinery room. As a best practice, we use the smoke test to develop a ventilation system diagram that visually depicts the function of the system.


It is important for ammonia refrigeration facilities in California to be aware of the requirements of Title 8 CCR §5143. We suggest that annual airflow tests be incorporated into the facility inspection, testing, and maintenance program for other refrigeration equipment onsite. A ventilation test can be readily integrated into other annual tests such as B109 inspections, ammonia detection/alarm tests, and e-stop tests.

[1] 1967 UMC §1508

Leave a Reply

Your email address will not be published. Required fields are marked *