Appropriate ventilation is essential to maintain safety in labs. However, it can use huge amounts of energy, particularly when used inefficiently. Therefore, it is essential that labs work to reduce the energy used for ventilation, where possible.

Download a fume-hood-energy-saving poster to use in your lab.

Use ventilation safely

Reducing the University's carbon footprint is important, but you must follow these guidelines when performing any actions in your lab regarding ventilation:

Using fume hoods efficiently

Over a year, a single fume hood can use around the same amount of energy as three average UK households. Therefore, labs that use fume hoods (and other ventilation) can play an important role in helping reduce the University’s carbon footprint and energy bill.

Making sure that your lab ventilation is working efficiently will also keep you as safe as possible.

Shut the sash

One of the most effective ways to reduce energy consumption is to lower the sash height whenever possible. When done well, this can save around £1,000 in energy costs each year for every fume hood.

You should close Variable Air Volume (VAV) fume hood sashes as much as possible. This can reduce energy consumption by 40 to 75%. You should only open VAV fume hood sashes to set up and perform experiments.

You can install motion-detector alarms to alert users when sashes are open on unoccupied fume hoods. This can reduce sash opening by up to 96%.

Please contact leaf@bath.ac.uk if you'd like stickers to remind users of best practice.

Maximise efficient airflow

Maintain a ‘free air flow zone’ in front of your fume cupboard at all times. This allows for effective airflow into the fume cupboard and safe containment.

Don't hang lab coats on gas taps or overcrowd the outside of the fume cupboard with equipment. This causes turbulence, making the fume cupboard less effective.

Switch off when possible

Turn biological safety cabinets and fume hoods off when not in use (where feasible and safe to do so). If they have an occupancy switch, turn them off. If not, consider reducing the exhaust when not in use, such as at night and during weekends.

You should lock and decommission unused fume hoods to prevent unnecessary energy use.

Load efficiently

Do not store hazardous items in fume hoods. Instead, store them in ventilated cabinets, which use 99% less energy.

Load your fume cupboard efficiently to allow for optimum airflow, safety, and energy efficiency. You should:

keep cills clear
place equipment 15cm behind the sash line, 10cm from the rear and sides of the cupboard and with 2.5cm gaps between items
avoid putting bulky items in your fume cupboard
raise items from the cupboard floor

Poorly-spaced or heavily loaded fume cupboards can cause 'dead spots’ with low face velocities at certain grid points due to airflow obstructions. To compensate, fume cupboards increase the airflow volumes by recalibration to try and achieve the target face velocity. The more loaded fume cupboards are, the more compensation will be required, leading to wasted energy. As such, adequate loading can reduce energy usage by 10 to 25%.

Maintain appropriate face velocities

What is appropriate for your fume cupboard will depend on safety requirements and manufacturer guidelines.

For many activities, face velocities around 0.5 metres per second or less can ensure containment. To review face velocity, you should consult with both energyteam@bath.ac.uk and your technical team for health and safety.

Higher face velocities may be required where there are highly hazardous materials, such as radioisotopes. However, higher face velocities are not necessarily better. In some cases, excessive velocities (greater than 0.7 metres per second) can induce turbulence, which will decrease containment. Ideally, fume cupboards should be checked annually to ensure the face velocities are still operating correctly and efficiently.

Low-flow fume cupboards can operate at lower face velocities, providing energy savings of up to 40%. They are designed more aerodynamically than standard fume cupboards and therefore can operate at a face velocity of 0.3 metres per second while providing the same safety.

Constant Air Volume (CAV) versus Variable Air Volume (VAV) models

We currently have two types of fume hood:

CAV fume hood models draw a similar air volume through the cupboard regardless of sash height
VAV fume hoods can adjust air flow depending on the sash height, greatly reducing their energy demand

If you are purchasing a fume cupboard, you should replace CAV fume hoods with VAV models (where infrastructure is suitable). However, retrofit kits may be a cheaper alternative to introduce VAV functionality to an existing CAV model but if your fume cupboard has less than 10 years of usage remaining, it may be better to replace them.

Biological safety cabinets

Recirculating units are more energy-efficient than ducted units but you must prioritise safety requirements. Please seek advice from your technical team. In addition to this:

make sure internal lights are LEDs
turn off cabinets when they're not in use
use a booking system to make sure individual users are responsible for turning off their cabinets after finishing their tasks

Using lab ventilation sustainably

Guidance on how to use ventilation in our labs as sustainably and efficiently as possible.