An air-con con?

YOUR response to the email from Gordon Bell regarding air conditioning (Readers’ Platform, May issue) gave me pause for thought.

I am in agreement with Gordon regarding the effectiveness of any air filtering, and would suggest that filtering capable of removing any residual Covid germs would certainly not be fitted in a conventional air conditioning unit.

The main reason for recirculating the air is one of cost (and profit), as the units are deliberately designed taking into account the recirculation, thus enabling the units to be relatively effective with smaller heating and refrigeration capabilities than would be required if the units were dealing only with fresh air.

At one time, though, wall units were popular because they were made in Spain and other countries for a market where the ambient temperatures were higher than is the norm in Britain. The units were relatively cheap, having less need to deal with a large temperature range. These units fell out of favour when faced with our cold wet winters.

Turning to the studies you mention, I find these somewhat bizarre. The figure for the risk of catching Covid on board a train of 1-in-11,000 journeys would suggest that someone commuting five days a week, 48 weeks in a year should catch the infection after 20 years!

I would respectfully also suggest that air being distributed by a fan would be far more effective at moving the germs about than the force of convection.

Malcolm Storey

By email