Air exchange rate in the laboratory – A guide to laboratory ventilation

A sophisticated ventilation concept plays a central role in the laboratory to protect laboratory staff from harmful vapours and particles. A key requirement for this is not only ensuring the right air exchange, but also a suitable supply air system that ensures mixing of the room air.

However, room ventilation systems in the laboratory have huge energy needs: Just a single laboratory fume hood can consume the same amount of energy as up to three detached houses.

To minimise resources and save costs, it is therefore worth optimising the ventilation concept and the air exchange rate in the laboratory. Read on to discover how to achieve this.

What does air exchange rate mean?

The air exchange rate or air exchange coefficient is an indicator showing how often the room air is exchanged in an hour.  It is expressed as 1/h or h-1 (pronounced “per hour”). It is also known as ACH, or “air changes per hour”.

By way of example, an air exchange rate of 3 1/h means that the room air is completely changed 3 times an hour.

For hygiene reasons, the minimum air exchange in internal rooms according to DIN EN 12831 is usually 0.5 1/h. This means that in order to maintain hygienic conditions, the air must be completely exchanged every 2 hours.

However, this minimum value only applies to simple living spaces or offices. A laboratory needs to meet higher standards – due to the frequent handling of toxic, pathogenic or other harmful substances. The staff working in such facilities need to be protected from all of these hazards.

To ensure Safety in the laboratory, the ventilation system needs to be powerful enough. Various factors determine how effective it needs to be:

• Laboratory size and number of workstations: The overall size of the laboratory and the number of workstations determine how much air needs to be extracted.

• Temperature contribution of equipment: Use of laboratory equipment often results in high thermal loads.

• Partial flows of extract air volumes through the laboratory equipment: All fume hoods, safety cabinets, etc. must be included in the overall ventilation concept.

• Moisture loads: Moisture expelled into the room air by people, processes or equipment can also be an influencing factor.

• Pollutant load: Above all, however, the materials and substances used in the laboratory are the decisive factor particularly effective extraction. when it comes to air exchange. Substances that irritate the respiratory tract, for example, require particularly effective exhaust air.

Standards & regulations: What should the air exchange rate be in the laboratory?

The applicable standards and regulations surrounding air exchange vary from country to country. Since 2020, a standard for the entire EU region has been in planning: the CEN/TS 17441 (laboratory facilities – ventilation systems in laboratories), which currently still has the status of a preliminary standard. It replaces large parts of the previous standard DIN 1946-7 (Room ventilation systems in laboratories).

In Germany, the regulations contained in TRGS 526 "Laboratories", as issued by the German Federal Institute for Occupational Safety and Health (Bundesanstalt für Arbeitsschutz und Arbeitsmedizin, BAUA). This specifies a value of 25 m³/h for each m² of laboratory area.

At a room height of 3 m, this results in the previously mentioned air exchange of 8 1/h. Sometimes, however, significantly higher air exchange may be required, particularly where highly toxic substances are used.

In some cases though, the air exchange in the laboratory may even be reduced. This may be the case if a risk assessment has concluded that the lower amount of ventilation is sufficient for the planned activities.

For laboratory operators, this means: Flexible ventilation offers significant savings potential. However, the overall concept should be considered, which involves more than just air exchange.

Overall concept for laboratory ventilation

As mentioned at the outset, an air exchange of 25 m³/m2h is a baseline for planning. In practice, this means: A tailored risk assessment is necessary to properly plan the room ventilation systems in the respective laboratory.

The air not only needs to be supplied and extracted at a sufficient volume – but it is crucial that the room air is also mixed properly. The supply air system should be designed such that hazardous materials are unable to accumulate in one area and thus potentially endanger laboratory staff.

For this reason, it is always advisable to consult a professional in laboratory planning, particularly when it comes to the right ventilation.

Calculating the air exchange rate in the laboratory

With the above planning baseline of 25 m³/m2h, even a layperson can roughly calculate the ventilation rate. However, this is just a rough estimate to serve as a guide.

The air exchange rate in the laboratory can be calculated using the following formula:

A simple calculation: A laboratory with 100 m² of floor space and a room height of 3 m is ventilated with an air flow of 25 m³/m2h.

1. First, the exhaust air volume is calculated for the overall floor space:
   Area 100 m² x extract air volume flow 25 m³/h = 2,500 m³/h

2. Then the room volume:
   Area 100 m² x room height 3 m = 300 m³

3. This results in the air exchange rate:
   Total extract air volume flow 2,500 m³/h / room volume 300 m³ = 8.33 1/h

Conversely, you can also calculate the extract air volume flow using the air exchange rate, i.e., how many cubic metres of air the ventilation system should replace per hour. In this case, the calculation is as follows:

If the laboratory is operated continuously for 24 hours based on this sample calculation, this would mean an air volume of around 60,000 m³ would need to be exchanged each day. A lot of energy is required to move such a volume of air. This is why laboratory ventilation is a key element when it comes to saving energy and costs.

Air exchange in the laboratory as an environmental and cost factor

Although a high rate of air exchange in the laboratory ensures safety when combined with the right supply air system, it directly impacts the environmental balance and operating costs. The bigger the laboratory and the longer the daily usage times, the more intensive the air exchange. This drives up costs.

The required energy for heating and cooling also increases, because the supplied fresh air first needs to be brought up to temperature. Although a lower rate of air exchange would save energy and heating costs, it may pose a risk to the laboratory personnel.

It is important to strike the right balance between safety on the one hand and cost efficiency and preservation of resources on the other. Ventilation should be as low as possible without jeopardising anyone. Smart ventilation and air-conditioning technology helps considerably.

Specifically, these first three measures help to work both safety and energy efficiently:

Adjust the ventilation plan to individual requirements

Properly configured ventilation is a key aspect even at the planning stage of a laboratory. The first step is to conduct a comprehensive risk assessment: This should be as comprehensive as possible and incorporate factors such as: 

• Laboratory size, 
• Laboratory equipment (particularly fume hoods, safety cabinets, housings, etc.) 
• and the chemicals and processes used.

The supply air system should also be well planned: This should be designed so as to achieve the best possible mixing of room air with as little energy expenditure as possible.

A key factor is also how different ventilation zones are partitioned: In rooms in which less hazardous work is conducted, natural ventilation or less air exchange may suffice.

It is also advisable to install a flexible ventilation system from the outset, which can respond to the changing room conditions and safety requirements.

Reduce air exchange where possible

During day-to-day laboratory operations, energy can be saved by reducing the air exchange to the minimum required amount. For example, the air exchange rate can be reduced from 8 to 4 changes per hour if no hazardous materials are being released.

The ventilation should also be reduced if no-one is currently working in the laboratory, for example at night or during breaks. A standby mode for fume hoods is also worthwhile in order to minimise air flow when they are not being actively used.

Employees, too, can help save energy by immediately closing the sashes on fume hoods when they are no longer needed for example.

Using smart air management

A smart, demand-based ventilation controller offers the greatest potential – particularly in rooms that have very flexible uses.

A centrally managed control system ensures that the air exchange is dynamically adjusted. All fume hoods, extraction systems, ventilated laboratory cabinets, etc. are coordinated with each other and are regulated automatically according to use. This means the entire laboratory equipment helps to reduce energy needs.

Safety & efficiency: the perfect air exchange rate in the laboratory

To summarise, the right air exchange in the laboratory and a good mix of room air requires a combination of good planning and individual risk assessments, modern equipment, smart control systems, and employee awareness. This way, energy savings potentials can be fully realised without impacting safety.

A final tip: Don’t forget to have the ventilation systems maintained to keep them fully functional in the long-term and prevent unnecessary increases in energy demand.