I'm puzzled by this line in the Telegraph article :
"However, these “recirculated air” filters do not remove fumes or vapours from the engine. So if engine oil or hydraulic fuel leaks, toxic chemicals can contaminate the air supply."
The recirc filters (provided they are clean and serviceable) are capable of removing SARS virus and similar, suspended in the cabin air. How can they 'not' remove these chemicals ?
As I understood it from that BALPA Clean Cabin Air conference a few years ago, the much-maligned recirculation system is the only filtration system technically possible at the moment; once TCPs, pyrolytes etc have made it to the cabin the recirc filters will (eventually) remove them. I would have thought they'd catch toxic fumes too.