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What kind of filter can keep viruses out of the data centre?

As a company we have written and spoken many times about the need for ventilation in the computer room and general data centre environment.

We have talked about the need to reduce dust building up on equipment which causes it to overheat. We have spoken about the need to reduce Volatile Organic Components, VOCs, building up in the computer room which are injurious to health. We have written about the need to filter smoke from incoming air to prevent false alarms in sensitive smoke detection equipment and subsequent automatic fire suppression gas release.

We have plenty of guidance from standards that talk about four air changes per hour and advice from ASHRAE about MERV 13 filters (no relations to MERS) to maintain an ISO 14644 Class 8 level of cleanliness and air contamination.

In Europe we have used the European standard EN779 which proposes an F7 grade of filter as equivalent to the American MERV 13 but not many people in the industry seem to realise that standard was retired over a year ago.

The correct standard we should now be using is EN ISO 16890-1:2016 Air filters for general ventilation. Technical specifications, requirements and classification system based upon particulate matter efficiency (ePM)

This standard calls for removal of particles classified by size, i.e. 10 micron, 2.5 micron and 1 micron. In the new ISO 16890 standard filter efficiencies are determined with regard to the particulate classes PM1, PM2.5 and PM10, as well as coarse dust. The ISO 16890 standard is thus based on the same evaluation parameters used by the World Health Organisation, WHO, and other environmental authorities.

The numbers 1, 2.5 and 10 refer to the particle sizes in microns (millionths of a metre). PM1 includes smoke and viruses, PM2.5 includes bacteria and PM10 includes fungal spores and pollen. PM1 particulates are seen as particularly dangerous as they can enter the bloodstream directly through the lungs.

The obvious question on every data centre manager’s lips now is of course, ‘so what kind of filter do I need now, oh and did you just mention viruses?’

So how big is a coronavirus? It’s about a quarter of micron across. That’s smaller than the one micron rating of a PM1 filter but airborne viruses tend to hitch a lift on a five micron water droplet which somebody has just sneezed or coughed out. So the PM1 filter will take out a lot of viruses but we have to consider that when the water droplet evaporates the virus may be mobile again.

To meet the current World Health Organization guidelines we would recommend two stage filtering consisting of a first stage ePM2.5 65% and then a second stage ePM1>50%. The ‘percentage’ figures used here represent the efficiency of removal of the particles. 100% efficiency would be ideal but practically difficult.

This combination will take out dust, smoke, bacteria and
some viruses.

If we really want to take out viruses then we need to go a step further to HEPA filters, that’s High Efficiency Particulate filters. We have a different standard for this; EN 1822-1:2019 High efficiency air filters (EPA, HEPA and ULPA). Classification, performance testing, marking.

HEPA filters are measured against 0.3 micron particles. A HEPA H13 filter will take out 99.99% of these and an H14 filter will take out 99.999%. At the top of the tree we have a U15 Ultra Low Particulate filter that will take out 99.9999% of 0.14 micron particles.

To conclude: A two stage ePM2.5 65% and then a second stage ePM1>50% filtration system will meet WHO guidelines for personal health and take out all contaminants and some viruses.

An H14 filter will take out viruses. Note that the finer the filter then the more power it will take to blow a big volume of air through it and the more often it will need to be changed. There are significant consequences to going to this stage of filter.

When changing an ePM1 or HEPA filter it must be treated as biologically contaminated waste and removed whilst wearing gloves and an FFP3 face mask: bag and seal the filters immediately. At the end of the shift bag the gloves and face mask as well.

Please note that this our interpretation of the standards and publicly available information relating to viruses and filters. We make no recommendation or guarantees that utilising these filters will offer an protection against viruses. Seek the help of a health specialist if that is your primary goal.