47 36. In addition to the avoidance of the risks of positional asphyxia referred to above, the CPT has systematically recommended an absolute ban on the use of means likely to obstruct the airways (nose and/or mouth) partially or wholly. Serious incidents that have occurred in various countries over the last ten years in the course of deportations have highlighted the considerable risk to the lives of the persons concerned of using these methods (gagging the mouth and/or nose with adhesive tape, putting a cushion or padded glove on the face, pushing the face against the back of the seat in front, etc.). The CPT drew the attention of States Parties to the Convention to the dangers of methods of this kind as far back as 1997, in its 7th General Report. It notes that this practice is now expressly prohibited in many States Parties and invites States which have not already done so to introduce binding provisions in this respect without further delay. 37. It is essential that, in the event of a flight emergency while the plane is airborne, the rescue of the person being deported is not impeded. Consequently, it must be possible to remove immediately any means restricting the freedom of movement of the deportee, upon an order from the crew. Account should also be taken of the health risks connected with the so-called “economy-class syndrome” in the case of persons who are confined to their seats for long periods1. 38. Two particular points were of concern to the CPT after visits to certain countries: the wearing of masks by deportation escorts and the use, by the latter, of incapacitating or irritant gases to remove immigration detainees from their cells in order to transfer them to the aircraft. In the CPT’s opinion, security considerations can never serve to justify escort staff wearing masks during deportation operations. This practice is highly undesirable, since it could make it very difficult to ascertain who is responsible in the event of allegations of ill-treatment. The CPT also has very serious reservations about the use of incapacitating or irritant gases to bring recalcitrant detainees under control in order to remove them from their cells and transfer them to the aircraft. The use of such gases in very confined spaces, such as cells, entails manifest risks to the health of both the detainee and the staff concerned. Staff should be trained in other control techniques (for instance, manual control techniques or the use of shields) to immobilise a recalcitrant detainee. 1 See, in particular, “Frequency and prevention of symptomless deep-vein thrombosis in longhaul flights: a randomised trial”, John Scurr et al, The Lancet, Vol. 357, 12 May 2001.