4.3 Ventilated workstations

Regulations for work involving fume hoods/benches

Work involving fume hoods and fume benches is affected by various factors, including the surrounding environment, individual work methods, and the design of supply and extraction air systems.

Incorrect work methods can easily compromise the effectiveness of fume hoods and fume benches, leading to reduced safety.

Fume hoods and fume benches are equipped with controls and alarm functions that warn users when the extraction airflow rate is too low. Regular maintenance and repairs of fume hoods and fume benches are conducted by facilities management.

The following rules ensure safe work practices, reducing the risk of leakage and harmful exposure.

Rules

Supervision of flammable materials: Laboratory setups involving open containers with flammable materials (i.e., not closed assemblies) must be supervised by staff. This precaution is necessary in case a loss of ventilation poses a risk of creating an explosive atmosphere
Electrical and ventilation outages: During electrical or ventilation outages, close all containers with flammable material, shut down heating in the laboratory setup, and then close the hatch. For more information see section 9.1 Plans of action for power and/or ventilation failure.
Electrical equipment in fume hoods: Electrical equipment within the fume hood should only be connected via interlocked electrical power outlets. Electrical power to these outlets is automatically interrupted in the event of ventilation failure. However, electrical equipment marked with an EX-classification sign (as shown below) is an exception to this rule.
EX-classification instruction: Follow the EX-classification instructions for both the fume hood and the laboratory. These instructions specifyzones where only electrical equipment marked ‘EX’ is permitted, with no exceptions allowed. For more information see section 5.2.1 EXclassified areas.
Power socket placement: Power sockets should never be placed inside, under, or in front of the fume hood.
Handling corrosive acids: Acids that produce corrosive gases or fumes, such as perchloric acid, aqua regia, and concentrated hydrochloric acid, must only be handled in special, flushable fume hoods. For more information see section 5.6 Corrosives.

EX-classification sign. Illustration. — EX-classification sign.

Fume hood

Adjust the hood sash position: When using the fume hood, ensure that the hood sash (or hatch) is positioned as low as practically necessary. The recommended maximum opening is 30 centimeters. The sash serves as a physical barrier in case of accidents. Remember to keep the sash closed when you are not actively working inside the hood.
Work deep inside the fume hood: Whenever possible, perform your work deep within the fume hood.
Minimize clutter: Avoid cluttering the fume hood with unnecessary bottles or equipment. Keep the workspace clean and clear. Only materials actively in use should be present inside the hood.
No storage of chemicals: Do note store chemicals or any other items within the fume hood.
Energy saving: Save energy by closing the fume hood hatch when no work is being carried out.

Fume bench

Appropriate use of fume benches: Fume benches should only be utilized for cold work (temperatures below 50°C).
Perforated surface clearance: Ensure that two-thirds of the perforated surface remains free.
Contamination placement: Place any source of contamination at least 10 centimeters behind the perforations.
Protective covers: Fume benches can be equipped with protective covers, enhancing safety. A protective cover enhances safety by increasing the height, allowing for a larger portion of the perforated surface to be used as a work area.
Height considerations: If protective covers are not used, avoid placing any contamination source higher than 15-20 centimeters above the work surface. Maintaining this height restriction ensures safety.
Clean perforated surface: Regularly clean the perforated benchtop surface to remove dirt, dust, and chemical debris. Accumulated debris can block airflow, and lead to lesser protection.

Glove box

In addition to fume hoods, some laboratories use contained glove box units for working with reactive chemicals in an inert environment, handling very toxic substances within a completely closed system, or creating a stable, draft-free setup for weighing hazardous or reactive materials. These units can be very effective because they offer complete containment.

If you haven’t previously used a particular glove box, it’s essential that you consult with the person responsible for that glove box before attempting to use it.

Keep in mind that the glove box is a shared space used by members from various groups.

Determine what types of materials or chemicals that can be stored within the glove box.
Label everything you intend to keep in the glove box and place it in a storage container.
Remove chemicals or reagents that are no longer required.
Promptly remove waste and prevent it from accumulating.
Appropriately label hazardous waste containers within the glovebox at all times.

Local exhaust ventilation

Place the local exhaust ventilation point as close as possible to the contamination source. The maximum allowable distance should be equal to the diameter of the extraction tubing.

LAF bench

Open Laminar Air Flow (LAF) benches are used for product protection during sterile work, while closed LAF benches are used to protect both the product and the operator. The LAF bench should be connected to the exhaust ventilation system.

Note! If personal protection alone is required, a fume hood or bench always provides the best protection.

Local exhaust ventilation in a laboratory. Photo. — Local exhaust ventilation.