Importance of Airflow Monitors for Fume Hoods

by Gary Holland

Laboratory safety encompasses many diverse aspects. From an HVAC standpoint, the most common is the Fume hood. Laboratories of all types utilize fume hoods as a means of protecting their employees or students and the processes and experiments that are performed. How can the person responsible for safety in the laboratory be sure that employees are being protected—all the time—from potentially hazardous fumes?

For many years, the inclusion of an airflow alarm, or monitor (see Figure 1), has been recommended.
Most specifications addressing an alarm on a hood referred to one or more regulatory guidelines that suggested that a monitoring device be included with the fume hood, at least on new and remodeled hoods.

The most commonly referenced guidelines were from such diverse organizations and publications as:

• National Research Council—Prudent Practices ForHandling Hazardous Chemicals In Laboratories, 1981
• NFPA—Fire Protection For Laboratories Using Chemicals, 1981
• Public Works, Canada—Standards & Guidelines, 1988
• OSHA Lab Standard—Occupational Exposure to Hazardous Chemicals in Laboratories, 1991
• ASHRAE—Applications Handbook, 1991
• ANSI—Laboratory Ventilation Standard, 1992
• SEFA—Laboratory Fume Hoods Recommended Practices, 1992

Figure 1 Airflow monitors 33556-50 and 33556-60.

Of particular relevance are the dates of the above documents—all were published 12 or more years ago, with the exception of two that were published over 20 years ago. In the 1980s and early 1990s, the use of a fume hood as a primary safety device was still being refined. The same can also be said for the airflow monitor as an important safety accessory. The majority of the regulatory guidelines utilized language that recommended an airflow alarm, which was mandatory only in the case of a new or remodeled (i.e., moved to another location) fume hood.

While this was certainly a step forward in laboratory safety from a ventilation standpoint, good laboratory practices continued to evolve throughout the 1990s. Since then, many of these documents have been revised with stronger language regarding the need for an airflow monitor. Table 1 compares the original wording to the revised wording.

As regulations have been revised, qualifying conditions have been eliminated:

• No longer just new or remodeled hoods, but all hoods, with no exceptions
• No longer when an alarm is furnished, but all hoods, with no exceptions
• No longer a string or ribbon, but a real monitoring device that can indicate proper hood operation.

UPDATE ON RECENT REGULATION CHANGE--Last summer, the California Code of Regulations, General Industry Safety Orders, California Administrative Code ("Cal OSHA") was revised to read as follows:

“By January 1, 2008, hoods shall be equipped with a quantitative airflow monitor that continuously indicates whether air is flowing into the exhaust system during operation. The quantitative airflow monitor shall measure either the exact rate of inward airflow or the relative amount of inward airflow.”

The wording of each regulatory guideline that changed in recent years now applies simply to “all hoods.” These changes were made to improve laboratory fume hood safety. Conscientious safety officers, industrial hygiene professionals, and laboratory supervisors would agree with the industry experts on the committees of the above organizations that providing the safest working environment possible for all laboratory occupants is of utmost importance. A monitor on each fume hood is the logical conclusion.