The Role Of Fume Hood Exhaust Fans

If your workspace deals with toxic chemicals, chances are, you know the importance of a fume hood.

Installing this ventilation device is a major and necessary purchase for your operation. Delaying the purchase of a fume hood or buying the wrong type for your needs may not only break several federal and state regulations, but also expose your workers to toxic substances that can have dangerous implications.

Here is what you need to know about the role fume hood exhaust fans play in a workspace, including:

• How they work
• When they should and shouldn’t be used
• Why workplace practices matter when it comes to usage

How Fume Hoods Work

A reliable engineering piece often found in labs, fume hoods remove vapors, dusts, gases and fumes that are created within the hood. As air flows into the hood, an exhaust fan system removes these toxic chemicals.

There are two types of fume hoods commonly used today: Ducted and ductless. Though they both have the same goal, how the process is carried out differs between the two.

Ducted fume hoods have ventilated enclosures and operate within the framework of your building’s infrastructure. They pull toxic fumes out of your laboratory through an HVAC system.

They are designed using a base, work surface, hood, blower and ducting that carries the exhaust fumes outside. Whether your ventilation system has enough air to provide the correct volume of ventilation to the hood is important to consider when determining which ducted fume hood to purchase.

Ductless Fume Hoods

Ductless fume hoods, on the other hand, operate off a carbon filter system. This recirculates filtered air back into your laboratory.

Unlike ducted fume hoods, this type of hood is self-contained. Laboratories or facilities where mobility is necessary find ductless fume hoods to be more accommodating. They also can be used in laboratories that handle light to moderate chemical loads (no more than 10 chemicals per application, with a volume of approximately 500 mls or less).

More information about the differences between these two types of hoods can be found in our article, Laboratory Fume Hood: Ducted Vs. Ductless, including the advantages and disadvantages of each.

When Fume Hoods Should And Shouldn’t Be Used

Though a laboratory is one of the most frequent users of a lab hood, other industries implement their use in production as well, such as forensics and industrial operations.

A fume hood often is the main component that protects workers who are handling flammable or toxic chemicals. Some situations where a fume hood’s exhaust system is critical include:

• When working with inhalation hazards, such as chemical vapors, radioactive materials, and toxic gases and powders.
• When procedures may expose workers to substances that could explode or cause a change in pressure.
• When vapors may cause fires.
• When an offensive odor is produced as workers are managing chemical compounds.

Though the above outlines some of the situations where a fume hood should be used, there are some instances when one shouldn’t be used.

For example, during a power outage, it is likely the ventilation in a workspace will not function properly. Because a fume hood relies on exhaust fans to remove toxic substances from the area, operating a fume hood during a power outage could pose a danger to workers.

It’s also possible that your particular lab might require a specialized design for your fume hood, depending on the chemicals your workers handle. For example, fume hoods can be designed with various surfaces for chemical resistance.

Why Workplace Practices Matter

Fume hoods offer an excellent source of protection against toxic chemicals and substances because of their effective exhaust systems. However, if not used or maintained properly, their effectiveness will suffer because the exhaust system may not completely remove dangerous particles that are present.

Implementing procedures at your workplace that ensure fume hoods are properly maintained and used is essential to following state and federal regulations, as well as protecting your workers.

Before beginning work, one of the most important practices lab technicians should conduct is to ensure the exhaust fan is working. The exhaust system performs the main job of a hood, so if not working properly, the hood will not operate effectively. To do so, they should check:

• The baffles, which are the movable partitions that create openings in the back of the hood. These keep airflow uniform, which increases efficiency.
• For any obstructions, to ensure airflow is not impeded.
• The airflow monitor, if part of the hood’s design. Checking the status of the airflow monitor is important because the device will alert you if any suspected changes in airflow occur.

The following are some further examples of routine practices that should take place to ensure a fume hood operates efficiently and safely:

• Follow manufacturer’s guidelines regarding the placement of apparatus. In general, all work should be conducted and all apparatus should be kept at least 6 inches back from the hood’s face.
• Keep the fume hood’s sash between you and the work you are conducting.
• Remove any obstructions from the hood slots and baffles to ensure good airflow remains.
• Follow proper laboratory design to reduce outside airflow influences, such as positioning the fume hood away from doors and minimizing foot traffic patterns.
• Do not store chemicals or lab equipment in the hood. If large equipment must be stored in the hood, place pieces on blocks to allow air to flow under the equipment.
• Avoid sources that may cause a spark inside the hood, including electrical receptacles.

Low exhaust airflow and any other mechanical problems that occur in a fume hood can instantly create hazardous conditions for workers. It’s important that hood users report any problems immediately and contact your fume hood’s manufacturer for instructions on how to resolve.

Our article, How To Use Your Laboratory Fume Hood Effectively, provides more tips on how to minimize air disturbances and follow operating procedures in your workspace.

Bottom Line

Sorting through your options can be challenging. Quality fume hood manufacturers can help you determine which type of fume hood is best for your workspace, including:

• Whether a ducted or ductless fume hood exhaust system is a better fit for your operation
• Which specifications meet the requirements of your lab, including:
• Hood size
• Surface material
• Surface fixtures
• Color options
• Base cabinets and accessories
• Any other special requirements based on the chemicals used in your space
• Which choices meet your budget

With the right fume hood, your workers will enjoy a well-designed workspace that prioritizes safety and efficiency - while you enjoy peace of mind that your customized needs are met in a timely and cost-efficient manner.