Data centre economisers and air cleanliness need to be considered together. Air-side economisers can reduce cooling costs by using outside air when conditions allow, but filtration and contamination control are important when that air enters a data hall.
How do air-side economisers work?
An air-side economiser uses suitable outside air to help cool the data centre, reducing the need for mechanical cooling. Depending on the system design and outside conditions, the incoming air may be mixed with recirculated air before being supplied to the IT environment.
This approach can reduce energy consumption, but the quality of the incoming air depends on factors including:
- The location of air intakes.
- Outdoor pollution and nearby activities.
- Filter selection, condition and maintenance.
- The volume of outside air entering the system.
- The operation and condition of the air-handling equipment.
Water-side economisers operate differently and do not introduce outside air directly into the data hall through the cooling process.
What does the research say?
Researchers at Lawrence Berkeley National Laboratory studied particle concentrations in eight operating data centres in Northern California. Their research found that the data centre using outside air for cooling experienced substantially higher particle concentrations when ventilation rates were high, although the measured concentrations remained below the industry limits considered in that study. Systems & Energy Technologies Analysis
In a separate study, the researchers found that improved filtration used with an economiser reduced the ratio of indoor to outdoor particles to levels similar to those seen with conventional filtration and cooling. The study also found that, at the data centre examined, cooling energy savings outweighed the additional fan energy associated with improved filtration. Systems & Energy Technologies Analysis
These studies demonstrate that outside-air cooling and good contamination control can work together. They also show why filtration should be considered as part of the overall cooling strategy. The findings relate to the sites and conditions studied; each data centre needs to assess its own design and operating environment.
Where can contamination come from?
Potential sources of airborne particles include road traffic, construction, industrial activity and other outdoor sources close to air intakes.
Particles can also arise inside the facility. Examples include wear from mechanical components, maintenance activities, packaging, construction work and contamination brought in on footwear or equipment.
The appearance of dust alone does not reliably identify its source. Where the source is uncertain or contamination is recurring, sampling and laboratory analysis may help establish what is present and support an investigation.
Airborne cleanliness and surface cleanliness are different
ISO 14644-1 classifies air cleanliness according to the concentration of airborne particles at specified particle sizes. A room that achieves ISO Class 8 during a test has met the relevant airborne classification criteria under the conditions and at the time it was tested.
That result does not, by itself, establish that all surfaces are free from deposited dust. A data hall can achieve the required airborne classification and still have visible or accumulated contamination on cabinets, equipment and other surfaces.
For that reason, IT Cleaning Ltd considers both:
- Airborne particle levels, assessed through appropriate particle testing.
- Accessible surface cleanliness, assessed through inspection and technical cleaning.
Looking at both provides a more complete picture of the environment than either measure alone.
Why humidity matters
Temperature and humidity form part of the overall environmental conditions in which IT equipment operates. Humidity can affect the behaviour of some contaminants, while conditions outside equipment manufacturers’ specified limits may increase the risk of damage.
The Berkeley researchers found that humidity could be controlled within the recommended levels used in their study, including in the facilities using economisers. However, operating conditions and control strategies will vary between sites. LBL ETA Publications
Operators should follow the environmental requirements for their installed equipment and review temperature, humidity, filtration and contamination together.
What do equipment manufacturers require?
Manufacturers may specify environmental conditions for particular products and installations. For example, NVIDIA’s ConnectX-8 SuperNIC documentation states that, unless otherwise specified, NVIDIA products are designed for an environmentally controlled data centre with low levels of gaseous and particulate contamination. It says the operating environment should meet ISO 14644-1 Class 8 for cleanliness and ISA 71.04 severity level G1 for gaseous contamination. docs.nvidia.com
Requirements vary between products, so operators should check the current documentation for the equipment installed. An environmental requirement should not automatically be interpreted as a manufacturer’s requirement to use a particular cleaning contractor or cleaning frequency.
A practical approach to contamination control
Data centre operators and facilities teams can reduce uncertainty by reviewing:
- Air intake locations and local conditions, including nearby sources of pollution or construction.
- Filtration selection and maintenance, taking advice from the ventilation system designers and filter specialists.
- Airborne particle levels under representative operating conditions, including economiser operation where appropriate.
- Accessible surfaces and equipment air paths for signs of deposited contamination.
- Recurring contamination, investigating the source rather than relying on repeated cleaning alone.
- Equipment manufacturer requirements for air quality, temperature and humidity.
Technical cleaning can remove accumulated contamination and support a wider environmental control programme. If contamination continues to enter or be generated within the facility, its source also needs to be addressed.
Specialist data centre cleaning and particle testing
IT Cleaning Ltd provides specialist technical cleaning and airborne particle testing for data centres, data halls, server rooms and other critical IT environments.
If you are concerned about dust accumulation, air cleanliness or the condition of your data centre, contact IT Cleaning Ltd to discuss your requirements.
Further reading:
- Data Center Economizer Contamination and Humidity Study — Lawrence Berkeley National Laboratory
- Particle Concentrations in Data Centers — Lawrence Berkeley National Laboratory
- Can Combining Economizers with Improved Filtration Save Energy and Protect Equipment in Data Centers?
- NVIDIA DGX SuperPOD: Planning a Data Center Deployment