Fume Hood Monitors Should Play Larger Role In Lab Safety Plan, Reports Say

Over the past 10 years, regulatory and professional agencies have issued increasingly strong statements recommending that lab managers equip fume hoods with airflow monitoring devices. Although these monitors are not yet required, at least six standards have addressed the need for them. Despite these recommendations, thousands of fume hoods still do not have air flow monitors. This may change within the next few years, as the American National Standards Institute is expected to release a revised standard that requires lab managers to place monitors on all fume hoods.

Why Airflow Monitors?
Installation Barriers
Agency Recommendations
Redrafted Standard

Why Airflow Monitors? (Back to Top)
It is important to ensure that airflow moves in a proper, safe way through each fume hood in a lab because poor airflow can, in some situations, cause life-threatening accidents. In fume hood applications, airflow is stated in terms of face velocity. This is the speed (velocity) of air passing from the room through the front (face) of the hood and out the exhaust system to the outside environment.

Airflow is an important safety consideration in laboratories of all types because it prevents hazardous fumes from escaping fume hoods and permeating the air that researchers breathe. A face velocity of 80–120 linear feet/min is considered safe in most applications, although with proper HVAC controls and good laboratory procedures, a face velocity as low as 60 linear feet/min can be maintained.

Labs in North America use approximately one million fume hoods. This represents about half of the world's fume hood market, according to Gary Holland, business unit manager of the Controlled Environment Group at Alnor Corp. (Skokie, IL). More than half of the fume hoods in North America are thought to be equipped with either airflow controllers or airflow monitors, Holland says. Accurate statistics are not available for the rest of the fume hoods used around the world. Since the late 1970s, Alnor has developed airflow measuring instruments for laboratory fume hoods.

Installation Barriers (Back to Top)
Although airflow monitors seem like a logical feature for ensuring fume hood safety, several barriers often stand in the way of their installation. As with all purchases, funds must be allocated for the devices, which cost between US$300 and US$1000 each. Today, most managers purchase fume hood monitors when outfitting new laboratory facilities or retrofitting older facilities, as the cost can easily be absorbed in the construction budget. Other managers have purchased the monitors on a payment plan, installing one each month. The monitors are mounted to the fume hood through a 30-min installation process that can be performed by most building maintenance personnel. As the standards are recommendations and not requirements, managers and industrial hygienists must determine whether their labs require the devices.

"Occasionally lab researchers resist the monitors because they are perceived to be similar to smoke alarms that go off when toast burns," Holland says. "In most cases the researchers know what is causing the air flow problem, but are annoyed when the alarm goes off. Although they think the safety concept is a good idea, they can be frustrated with it in practice."

Labs that have not yet installed fume hood monitors usually perform spot airflow checks with thermoanemometers, rotating vane anemometers, or swinging vane anemometers. Each check takes only a few minutes to verify the airflow in a fume hood. However, the technique is not foolproof because there is no way to guarantee that airflow remains consistent between checks. The process is also not efficient, as it can be very labor intensive if there are a large number of hoods in the research facility.

Agency Recommendations (Back to Top)
Professional agencies and organizations have made three major, well-known recommendations and three less publicized recommendations to owners and users of laboratory fume hoods:

1982: The National Research Council published a landmark body of work covering laboratory operations that was titled Prudent Practices for Handling Hazardous Chemicals in Laboratories. This document has become a reference for many subsequent publications. It states that "Some continuous monitoring device for adequate hood performance should be present." This was the first reference to recommend a continuous airflow-monitoring device instead of periodic spot checks with handheld instruments.

1990: OSHA published a document titled Occupational Exposure to Hazardous Chemicals in Laboratories, also known as the Lab Standard. This recommended that lab facilities that were required to establish a Chemical Hygiene Plan use "A continuous monitoring device to allow convenient confirmation of adequate hood performance" on each fume hood covered by the plan. The Lab Standard took effect in January 1991 and has since been the standard for all lab operations in the U.S.

1992: The American Industrial Hygiene Association (AIHA) commissioned the American National Standards Institute (ANSI) to specifically address a number of operations issues within laboratories. The resulting document—ANSI/AIHA Z9.5 or the ANSI Laboratory Ventilation Standard—has been adopted by many progressive institutions as a good working model for adopting those elements required by the OSHA Lab Standard. The need for fume hood monitors was addressed in this document in the strongest possible terms, "New and remodeled hoods shall be equipped with a flow measuring device."

Other organizations with a working interest in laboratory facilities have also addressed the issue of fume hood airflow monitors, issuing these three specific recommendations:

1981: The National Fire Protection Assoc. published document NFPA 45, also called Fire Protection for Laboratories Using Chemicals. This said that, "Airflow indicators shall be installed on new laboratory hoods or on existing laboratory hoods, when modified."

1988: Public Works, Canada published Standards and Guidelines-MD 15128, declaring that "The annunciator (alarm) system shall include the following indicators and alarms:…adequate air flow and low air flow."

1991: The American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) Applications Handbook recommended that, "It is a good practice to equip laboratory fume hoods with alarm devices to detect failure of exhaust airflow."

Redrafted Standard (Back to Top)
A new version of the 1992 ANSI/AIHA Z9.5 or ANSI Laboratory Ventilation Standard is being redrafted. If it is passed as the draft is currently worded, it will make fume hood alarms mandatory in all labs. Holland says that he expects the new version of Z9.5 to pass within the next few years.

Even if the redrafted Z9.5 standard is passed, Holland says that the enforcement may be lax, as OSHA inspectors will not immediately visit all of the labs in the U.S. to confirm that they use the monitors. Rather, OSHA representatives will continue their periodic safety inspections and require labs to install monitors if they believe that their lab safety precautions are insufficient.

"Responsible people will install monitors." Holland says. "OSHA inspectors audit to the hygiene plan that the laboratories establish, so it will still be the responsibility of the labs to decide if they need to add the monitors to their hygiene plans. Lab safety managers understand the dangers that the monitors can avoid, though, so we continue to outfit more and more laboratories with the devices."

For more information, call Gary Holland at Alnor at 800-424-7427.

By Laura Vandendorpe