Increasingly IT Cleaning Ltd are coming across contamination on the underside of floor tiles, in the cold air plenum, and on the air tiles. One thing most of these data centres have in common is the use of economized air. It is therefore apparent that, whilst the incoming free air is filtered, it is not filtered low enough to remove all the particulate coming in with the air. This is leading to contamination of the cold air plenum and eventually the data centre, and equipment running within the data centre. The fact this contamination is airborne is being show by the relatively high readings we are getting at 0.5µm during our ISO 14644-3 survey. “Whilst theses data centres are passing often, they are only just passing at the 0.5µm level. This is worrying as if 0.5µm is high then 0.3µm is potentially even higher, although this level is not currently surveyed for ISO 14644-1 2015 Class 8, it could be leading to agglomeration of particles and damage to equipment” Stephen Yates. “The location of the inlet for the free air is also relevant, if they are located near a railway line for example, we find more dust that side than the inlet that is not over the railway. This is the same with carparks etc.” At IT Cleaning Ltd, we feel that data centres with economized air should increase their cleaning, to combat the ingress of particulate with the free air.