X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from [68.202.132.19] (account marv@lancaironline.net) by logan.com (CommuniGate Pro WEBUSER 5.1c.3) with HTTP id 1377630 for lml@lancaironline.net; Tue, 12 Sep 2006 14:57:06 -0400 From: "Marvin Kaye" Subject: Re: SUSPECT: High Altitude Oxygen Failure To: lml X-Mailer: CommuniGate Pro WebUser v5.1c.3 Date: Tue, 12 Sep 2006 14:57:06 -0400 Message-ID: In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain;charset="iso-8859-1";format="flowed" Content-Transfer-Encoding: 8bit Posted for "Lancair" : Mark, The small clear plastic masks that are found typically in light aircraft are not pressure masks. Their seal is quite imperfect and even the facial-hair challenged typically have leaks. They could be used above FL180 to our effective ceiling of FL290 providing you do not need to communicate a lot. The masks leak more with facial movement so you really need to be starting down if you have lost cabin pressure - and if non-pressurized ya really shouldn't be there long. There was a great article a few months ago in which a twin-Comanche pilot tried to extend his range by flying with a mask at FL250-270. He could not control his blood oxygen level and finally decided to come down, so I guess that he was not completely delirious. Values in the low 80's would get you critical care in an ER, and would get you into an ER if flying that way for long. The fast-donning masks that MH sells are about $5,000 and are required at higher flight levels (jet-jocky stuff). However pressure masks are not required below ~FL350. So says MH. Robert M. Simon, ES-P N301ES