2 October 2009
Having heard about your association on BBC Radio 4 ‘Today’ programme of 24 September, I am writing as a passenger as I thought you might be interested in my own experience of aircraft air filtration systems.
Around 10 years ago I had an upper respiratory tract infection which I thought I had ‘caught’ on a BA 747 long haul flight.
I wrote to BA and after many weeks received a reply, from the executive club or some-such.
The reply explained at great length that the air in the cabin was filtered through HEPA filters as used in hospital operating theatres and was therefore very clean indeed. As I have been in the cleanroom business for most of my working life, I knew something about HEPA filters and was quite surprised that the air quality still seemed poor.
On my next flight in a 747, I noticed that the outlet grilles were streaked with dirt in a way that should not have been possible with HEPA filtered air. It was then that I realised that although the recirculating air from the cabin might well have been through HEPA filters, the make-up air (outside fresh air) almost certainly had not. The streaks of dirt were presumably from the make-up air when the plane was on the ground rather than from the very pure air at altitude. I took photographs of the very visible streaks, wrote again, but to the best of my recollection received no reply.
With hindsight, I now see that the upper respiratory tract infection was more likely to have been an irritation from the make-up air rather than an infection from other passengers.
If the make-up air, which is untreated, can contain toxic substances, then it not surprising that passengers and especially cabin staff, who are subject to long-term exposure, report so many problems.
I hope that this is of help.