“If the airlines are already giving their passengers safe air, then why are they fighting regulations to that effect?”
Because they are ALREADY GETTING THE JOB DONE?
And who says they are fighting to stop people from getting filtered/fresh air?
PS: A fan is just a fan. It helps MOVE air. But I suspect Boeing - you know, the people who BUILD the plane? - know where the air is coming from! What do you think 100% fresh air means - open windows?
“It’s time we stop listing to the ‘happy talk’ of people who have stakes in trying to get people back in airplanes.”
It is time we stop listening to FrearBros who are terrified of getting out!
But I’m flying across the country next week. If I come down with coronavirus, I’ll let you know. Although it wouldn’t prove I caught it on an airliner, since I’ll be at greater risk when I go inside a WalMart!
If you are not reasonably safe on an airliner, then you aren’t safe in any store, restaurant, office, etc. Time to hide in the basement and wait until someone nukes us from orbit....
“The FAR 25 requirement for outside air for ventilation purposes is generally more than adequate for pressurization purposes as well; in the context of this discussion, pressurization is not a controlling factor for determining flow rates. The flow requirements needed to address the three remaining factors do not necessarily coincide. It was seen in a previous example that the required flow of conditioned air required for temperature control could be more than twice the FAR-specified value for outside air for contaminant control. The practice of recirculation was introduced to address this issue. As shown in Figure 2–4B, recirculation is accomplished by extracting air from the cabin and mixing it with conditioned outside air. Recirculation provides two benefits: it allows the total air flow rate to be higher than the flow rate of outside air, so good circulation in the cabin can be maintained independently of the flow of outside air; and the conditioned air is mixed with the comparatively warm recirculated air before being introduced into the cabin. Consequently, the conditioned air can be supplied at a much lower temperature (Ts in Equation 2–4) without causing discomfort from cold drafts, and the maximal flow rates of conditioned air required for temperature control can be reduced to match those required for contaminant control more closely.
Because recirculation removes air from the cabin and returns it to the cabin, it has no effect on average contaminant concentrations throughout the cabin, if it is unfiltered. Equation 2–2 still applies, and the average concentration of contaminants in the cabin air is determined by the flow rate of outside air, independently of the amount of recirculation. If the recirculation air is cleaned of contaminants, it has the same effect on contaminant concentrations in the cabin air as does clean outside air.
Current practice is to use only particle filters on recirculation air. Filter efficiencies are at least 40% (Mil Std 282) on the MD-80 series, but exceeds 93% on all other aircraft1 (Mil Std 282) (Boeing responses to NAS, April 10, 2001). Most aircraft manufactured more recently use HEPA filters. HEPA filters are highly effective (99.97% efficiency, Mil Std 282). Air filters are generally changed at the aircraft scheduled “c”-check, generally between 4,000 and 12,000 flight-hours (J.Lundquist, Pall Aerospace, personal communication, July 5, 2001). HEPA filters remove essentially all airborne pathogens and other particulate matter from an airstream that passes through them with a minimal efficiency of 99.97% for 0.3-µm particles. Although they are effective in removing particles, including bacteria and viruses, from the recirculated air and preventing their spread through the cabin by this route, they do not remove gaseous contaminants.”
https://www.ncbi.nlm.nih.gov/books/NBK207472/
“Air filters are generally changed at the aircraft scheduled “c”-check, generally between 4,000 and 12,000 flight-hours”
So about every 1 or 2 years. Wow, MUCH WORSE than I even thought. No wonder there are so many stories of people getting sick in these tubes on very long flights.
But thanks for the link anyway - the part that is REQUIRED by regulations pertains to the Oxygen partial pressure, and that is good. But it wasn’t written for viruses or filtration, which is understandable, as it wasn’t as big an issue in the past.
Anyway, the happy talk is also understandable - and if I were on Legal for an airline, I’d be telling them to say exactly the same. But the only way people can be CERTAIN that air isn’t being recirculated is when the regulations catch up with today’s conditions. Until then don’t expect much of a recovery, at all.