The Power of a Closed Sash: Maximising efficiency and safety in VAV Fume Hoods

In the world of laboratory work, safety and efficiency are non-negotiable. One of the most critical elements in this equation is the fume hood—a vital safety device designed to protect you from hazardous fumes, vapours, and particulates. But did you know that airflow is often the most energy-intensive process in laboratories across the UK?

To put this into perspective, a typical office requires 4 to 10 air changes per hour (ACH). In contrast, laboratory settings demand 6 to 30 ACH, depending on the nature of the work being conducted. So, why the need for such high ACH in labs?

Why High ACH Matters in Laboratories

High airflow rates are essential for several reasons:

• Safety First: Laboratories often handle hazardous chemicals and biological materials that can release harmful airborne contaminants. Increased ventilation is necessary to dilute and swiftly remove these substances, significantly reducing exposure risks for personnel.

• Preventing Risks: High ACH helps avoid the accumulation of flammable vapours, thereby mitigating fire and explosion risks. Compliance with regulatory safety standards set by organisations like the Health and Safety Executive (HSE) in the UK is also crucial.

• Improving Air Quality: Enhanced ventilation not only lowers levels of carbon dioxide (CO2) and volatile organic compounds (VOCs) but also helps regulate humidity, preventing mould growth.

• Maintaining Experimental Integrity: In sensitive lab environments, controlled conditions are vital to avoid interference with experiments and prevent cross-contamination. Effective ventilation supports the performance of fume hoods, which are critical for capturing and exhausting hazardous substances.

While I plan to dive deeper into general lab ventilation in a future post, today, let’s focus on how we can optimise our fume hoods to reduce overall energy demand. You might be surprised to learn that a single fume cupboard can consume as much energy as 3.5 houses (based on average UK 2-3 bedroom home)! Just think about how many fume cupboards are in your lab, department, or building—it's a staggering amount of energy!

Understanding Fume Hood Types: CAV vs. VAV

To effectively manage energy consumption, it’s essential to understand how fume hoods work. There are two main types: Constant Air Volume (CAV) and Variable Air Volume (VAV).

• CAV Fume Hoods: These maintain a constant airflow rate regardless of the sash position (the sliding panel that opens and closes the front of the hood). While they are simple and reliable, they can be less energy-efficient, leading to unnecessary energy use when the sash is closed or partially open.

• VAV Fume Hoods: These are designed to adjust airflow based on the sash position. When the sash is raised, airflow increases for adequate ventilation; when lowered, airflow decreases, resulting in significant energy savings. VAV systems are more energy-efficient and can provide better control of laboratory conditions.

Identifying Your Fume Hood Type

Wondering whether you have CAV or VAV fume hoods in your lab? Here are a few easy ways to tell:

1. Look for Airflow Monitoring Devices: VAV hoods typically have these devices that adjust exhaust airflow based on the sash position, often accompanied by a digital display showing real-time airflow rates or alarms for insufficient airflow.

2. Listen for Changes in Airflow Sound: When you adjust the sash, VAV hoods will produce a noticeable change in the airflow sound, indicating that the system is responding. In contrast, CAV hoods will maintain a consistent sound regardless of sash position.

3. Check Documentation: If you’re still unsure, your best bet is to consult the user manual or any documentation provided by the manufacturer, which should clearly specify whether your system is CAV or VAV.

Simple Steps for Energy Savings

Now that you know the difference between CAV and VAV hoods, let’s talk about an easy win for energy savings with VAV fume hoods: closing the sash! This simple action can lead to energy savings of up to 30%. Given that a fume cupboard can consume as much energy as 3.5 homes, you’re switching off an entire house just by shutting the sash! Not only does this practice promote sustainability, but it also enhances safety—sashes should always be closed when not in use.

Fostering a Culture of Safety and Sustainability

Changing behaviours around sash usage can be challenging, especially if your lab culture currently allows for open sashes. Here are some strategies to promote this change:

1. Educate Your Team: Host discussions or workshops about the benefits of keeping the sash closed, highlighting sustainability, safety, and improved lab quality. Use fun posters or digital messages to reinforce this message.

2. Install Instructional Signage: Place clear, eye-catching signs by the fume hoods as reminders to keep sashes closed. Ensure these signs stand out and complement your educational efforts.

3. Conduct Regular Audits: Consider informal audits to monitor sash status and share results with the team regularly. For even greater engagement, you could introduce a friendly competition or rewards for consistent compliance.

4. Apply the EAST Framework: Use the principles of EAST (Easy, Attractive, Social, Timely) to encourage behavioural changes. Create engaging challenges or incentives that align with these principles, making it easier and more appealing for lab members to adopt new habits.

Looking Ahead

There’s much more to explore regarding ventilation and fume hoods in future posts, including strategies for those with CAV hoods.

Action for the Week: Take a moment to make your team aware of the energy intensity of the fume hoods in your lab. Share how closing the sash on a VAV hood can save up to 30% of energy consumption. Develop a communications plan to encourage this crucial behaviour change!

By working together to optimise our fume hoods, we can create a safer, more sustainable laboratory environment for everyone. Stay tuned for more insights in our upcoming blogs!