3 Ways Fume Hoods Can Minimize Operational Exposure

There are risks associated with every kind of job, but when working with volatile or toxic chemicals, there is far more at stake. After years of working with chemicals, it's easy to let your guard down or for equipment to malfunction. Unfortunately, this can lead to dire consequences; occupational exposure is responsible for an estimated 3-6% of all cancers worldwide, according to the Centers for Disease Control and Prevention (CDC).

As the phrase suggests, occupational exposure is a term used to describe when a person is exposed to or comes into contact with harmful substances as a result of their profession. Fume hoods keep operators safe from exposure by protecting users from spills, harmful fumes, and even explosions. This can happen in any number of ways, but we'll review three main ways this can happen when working with this type of equipment.


Oftentimes, exposure can happen as a result of faulty or poorly maintained equipment. If a blower stops working in a fume hood, that can mean the air within the hood is not being properly directed away from the operator, resulting in an exposure. If blowers are not functioning properly, areas within the fume hood may not be properly circulated, resulting in dead air zones. Properly monitoring the airflow is a good way to avoid accidental exposure in the event of a blower failure.

The professional organization, SEFA (Scientific Equipment Furniture Association), in its recommended guidelines and best practices,  SEFA 1-2010 Section 4.1.10, specifies all laboratory fume hoods should include a monitor installed to verify proper exhaust flow and face velocity. Designed and engineered in each AirClean Systems' Fume Hood is a built-in airflow sensor to constantly monitor the face velocity and alert the end-user, via an audible and visible alarm, if the operating conditions become unsafe.

Regular maintenance is another vital tool in preventing equipment malfunctions. Testing should be performed, at a minimum, on an annual basis by a certifier to ensure proper containment and function. "Method of Testing Performance of Laboratory Fume Hoods" written by the American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (ASHRAE) provides guidance on testing methods for fume hoods as manufactured (AM), as used (AU), and as installed (AI) to help ensure proper containment and performance. Annual testing on flow visualization, face velocity measurements, and tracer gas containment can help ensure proper fume hood performance.

When using a ductless hood, unlike a traditional exhaust hood, filter replacement is key in ensuring user protection. If the carbon filter(s) are not regularly replaced, then contaminated air may not be treated, thus allowing toxic fumes and vapors to re-enter the laboratory. Many ductless fume hood companies incorporate electronic methods for filtration saturation detection while other companies recommend the use of colorimetric sampling tubes to determine filter life. AirClean Systems is one of those companies that incorporate an electronic method for filter life determination. 

Your safety and your employee's safety are important! Make sure your equipment is well-maintained and that it is functioning at peak performance every time you use it. It may feel like a bunch of pointless, repetitive checks, but your safety is worth the extra work.

Operator Error

It's not always the fault of the equipment when things go wrong. Sometimes it's our own mistakes that can lead to exposure to harsh or toxic substances. For example, it's never safe to store chemicals inside of a fume hood. The Occupational Safety and Health Administration's (OSHA) guidelines on Occupational Exposure to Hazardous Chemicals in Laboratories (1910.1450 Appendix A) states, "Toxic or corrosive chemicals that require vented storage should be stored in vented cabinets instead of in a chemical hood". This guidance is to prevent dead spots and areas of reduced airflow. The storage of large chemical volumes within the hood can also lead to accidental spills, increasing the potential of hazardous exothermic reactions. 

A fume hood is not designed for chemical storage but purpose-built chemical storage cabinets that are vented, non-vented, or filtered are acceptable methods for proper chemical storage. Standards such as NFPA45 (Standard of Fire Protection in Laboratories Using Chemicals) recommends storage or handling of no more than 5 gallons of hazardous chemicals without a proper storage cabinet. Filtered chemical storage cabinets are becoming more and more popular as an increased awareness of environmental contaminants are more in the headlines.

Other common user-related mistakes are raising the sash above the recommended operating level and peeking into the hood to gain an unobstructed view of what they are working with. While this may seem harmless, hoods are designed to provide protection at set operating heights, and fully opening the sash greatly increases the risk of exposure. SEFA 1-2010 Section 6.5.2 states "The user should never allow his head to break the plane of the sash because this will cause contaminated air to pass through the breathing zone." Care should be taken when working in a fume hood to avoid exposure from changes to the sash height or sudden movements.

Overcrowding your workspace can lead to exposure in unexpected ways. Cluttering your fume hood with various items can inhibit the flow of air and create eddy currents leading to dead areas in the hood. A general guideline outlined in SEFA1-2010 Section 6.51 is no more than 50% percent of the work surface should be covered by equipment or other obstructions.

Additional care should be taken when placing equipment inside of your fume hood. Equipment should be placed at least 6 inches back from the plane of the sash and 6 inches away from the sides of the unit. By keeping equipment a minimum of 6 inches away from the front plane of the sash , turbulence can be eliminated, and containment can be achieved.

The consequences of one mistake can be deadly to you or your coworkers. Always follow proper procedures when working with hazardous or volatile chemicals.

Wrong Equipment

Sometimes the problem stems from using the wrong equipment in an attempt to contain certain gases and fumes. Not every application may be appropriate for a particular fume hood or enclosure. Consultation with the fume hood manufacturer should be used to ensure the chemicals of concern are properly abated with the hood solution you utilize. A useful tool provided by SEFA for ductless fume hoods is the SEFA 9-A Section 5.3 application assessment form that promotes customer and manufacturer collaboration to approve the application before use. AirClean Systems is committed to the safe use of all its' filtered products and utilizes the application worksheet process to consult with prospective clients on the proper and safe use. When working with AirClean Systems you can feel confident that your application, and the recommended solution they offer, is right for your specific work process and overall safety.

Ultimately, your health and safety are of utmost importance. Don't let yourself become one more statistic of the hazards of occupational exposure; make sure you are maintaining your equipment, following proper protocol, and that you have the right equipment for every job. And if you are ever unsure about how to perform system checks, need advice on proper protocol, or just don't know if your equipment is right, be sure to give us a call at (919) 255-3220 or drop us an email at sales@aircleansystems.com; we're always happy to lend a hand to keep you safe.