It's never a good time for an inflight fire. Stoked by fuel or an electrical short, this nasty brand of emergency is near the top of most pilots' list of nightmares. But a cabin fire's consequences can be mitigated by using a smoke hood, which filters breathable air out of the poisonous plume of a fire, increasing the likelihood that the pilot can see and breathe long enough to put the airplane on the ground.
To be useful at all, a smoke hood must meet certain criteria: It needs to form an airtight seal around your head and neck, protecting your eyes, nose and mouth; it must be constructed of heat-resistant material such as Kapton; and it absolutely must feature a filter that brings in air from the outside into the mouth. The filter, usually made with activated charcoal, protects you against deadly carbon monoxide (CO) -- don't buy one that doesn't -- as well as particulate matter and other toxic gases. An effective smoke hood will catalyze CO to the more benign carbon dioxide (CO2). Standard gas masks don't do that, by the way.
Don't consider a hood that doesn't meet these basic safety criteria. High-quality smoke hoods will be certified by industry standards. While no UL testing has been performed on them, a multi-million dollar proposition in the U.S., European, Australian or Japanese standards are accepted in the industry for these products. Within the European CE testing protocol, an EN4 certification requires that the hood withstand 10,000 PPM of CO for at least 15 minutes. A CO concentration of 75 PPM can be disabling; 500 PPM is lethal.
Whether you're facing a CO leak or the full-blown cocktail of toxic gases, smoke and flames from an inflight fire, immediate and decisive action will save your life. Brent Blue, M.D., pilot and cofounder of Aeromedix (and the source for the Safe Escape smoke hood) says, "Smoke in a cockpit is so noxious, it's incapacitating. It's like being sprayed with pepper spray. It's incredibly irritating to your eyes, nose and lungs. Any smoke hood must cover your eyes so you can see."
Blue contradicts the old wives' tale that cabin smoke can be cleared by opening a window. "The increased air circulation may fan the fire and general aviation cabins aircraft are negatively pressurized so the air will come rushing in." An engine fire may enter the cabin through the firewall and from outside the fuselage if a window or canopy is open. The smoke hood is your safest option for getting on the ground in hostile cabin conditions.
The downside? Severe claustrophobia could exacerbate an already stressful experience and if you have significant lung disease, you may have difficulty drawing a deep breath while wearing a hood. However, that beats smoke inhalation, which causes half to 80 percent of fire-related deaths in the general population -- ahead of fire-related burns. Even sublethal levels of smoke and gases can seriously impair a pilot, enough to compromise flight safety. Hypoxia at higher altitudes can worsen the damage done by smoke.
A smoke hood completes the cabin environment trio; a high-quality CO detector (not a stick-on patch) and a Halon fire extinguisher should be available in your aircraft as well. (See the July 2003 Aviation Consumer for a review of Halon extinguishers and the November 2005 issue for the CO detector assessment.)
In our view, a detector that will sniff out CO ahead of the fact is preferable to donning a smoke hood and trying to filter the air after the fact. Similarly, a fire extinguisher may knock a fire down before it has time to make much smoke.
We were particular about the units we sampled -- only certified hoods with CO and toxic gas filtering made the cut. The three hoods we tested were the COGO ($119 from Safer America), the Parat-C (manufactured by German giant Draeger and sold for $198 by Safer America) and the Safe Escape Smoke Hood ($69.95 from Aeromedix).
We built a 6-foot-high, 2-foot-square framework of 1/2-inch PVC pipe, covered by 4-mil plastic sheeting. Three signaling smoke flares by Orion Safety Products created prodigious amounts of thick orange smoke, which contained 22 percent potassium chlorate (an eye irritant); the burning flare also produced carbon monoxide and nitrogen oxides.
We ignited one flare per hood and donned the hood as the flare was lit, simulating the suddenness with which an inflight fire can occur. There was no heat to the smoke, but it was plenty irritating. To measure the effectiveness of each mask's filtering capability, we took a baseline arterial blood oxygen saturation reading (SPO2) with a Nonin Onyx pulse oximeter. However, the pulse ox does not detect CO poisoning. CO binds to the hemoglobin in the blood, turning the cells as red as if they were oxygenated ... but they're not. Our baseline reading was 98 percent and the pulse ox determined whether the hoods delivered filtered oxygenated air as advertised. After stepping into the smoky booth, the plan was to stay there until the smoke dissipated, about two minutes. It mostly worked that way.
Tying long hair back will create a good seal with the hoods. We wore glasses during the test to determine whether they would be an obstacle to donning the mask quickly.
The Parat-C came tethered to the inside of a bright-yellow, plastic, zippered container, including directions that were large and easy to follow, but the detailed instruction sheet inside took some study. The hood worked like a champ. There was no sense of claustrophobia and the filtering kicked in immediately. The hood is made of a self-extinguishing PVC material, and the visor contains an anti-misting agent. Glasses and long hair fit comfortably in the hood and there was no impediment to donning it, which took only 10 seconds.
We were able to comfortably stand in the smoke chamber until the smoke dissipated and the pulse ox reading during this test was 97 percent. The Parat-C provides 15 minutes of protection from a variety of gases and smoke, including CO at 2500 PPM. It also filters toxins such as hydrogen cyanide, hydrogen chloride and acrolein, formed by the breakdown of some pollutants, such as gasoline.
The Safe Escape hood came next. Made of a flame-resistant, aluminum-foil cloth, it's designed to withstand up to 1400 degrees F. It comes in a compact, orange, plastic, zippered pouch that features detailed instructions in tiny print on one side and a graphical guide on the other. It's worth it to familiarize yourself with the instructions before you need them -- every second counts in a smoky cockpit.
The beefy zipper was easy to grasp and open quickly, an important feature, in our view. It was extraordinarily easy to put on and only required the removal of two red plugs from the filters inside and outside the mask. The clear face mask was generously sized and the interior mouthpiece connected to the filter was easy to use. This mask took a little longer to put on -- about 15 seconds -- due to monkeying around with the straps. While the mask worked just fine in clear air, we found it was necessary to pull the orange neck straps very snugly to keep the noxious gases out. After less than a minute in the smoke chamber, the straps that we thought were tightly snugged let some smoke in and we got a lungful.
It was not pleasant, causing throat irritation for hours. The pulse oximeter showed 94-percent saturation while in the smoke chamber and 96 percent after getting into the fresh air. Without operator error, the mask worked well, but it's crucial to tighten the neck straps completely to supplement the elastic neck band.
The Safe Escape comes with a five-year warranty from the date of manufacture and the manufacturer will replace the mask free of charge if you use it in an actual fire during that time. We think that's a good policy; although this is the least expensive of the three masks, the free replacement following real-life use should discourage hesitation in using it out of a sense of false economy. The manufacturer guarantees that the mask will give you 30 minutes of breathable air in a smoky or fiery environment.
The Israeli-made COGO was a contradiction. The foil-wrapped package comes in a canvas carry bag, but was very difficult to open without scissors and some tugging. We would be hard pressed to get it open in an emergency and would bring it on board already cut open. The directions on the packet were very clear.
Made of a vanilla-scented latex compound, it was a challenge to fit over a ponytail and especially difficult to pull over glasses. There would have been room for them inside, but the narrowness of the neck opening was an obstacle and it took two tries to get it on.
But once it was on, it was outstanding. The soft mouthpiece allows for rapid exhalation and prevents vapor buildup inside the mask. The tight neck fit kept the smoke out completely and filtration was excellent. Our pulse ox reading during the test was 96 percent and we felt no ill effects from the smoke at all.
Bonanza pilot John Whitehead had an electrical fire a few years ago and was struck that the cabin was completely filled by smoke within 30 seconds. "I could just see out the side windows ... and that was it," he told us. "Beside the lack of visibility, the horrid smell of the burning plastic wire was choking and distracting. A hood would have to be donned quickly to be of value."
Smoke hoods are only useful if you include them in your mental emergency preparation and if you can get to them reliably and quickly. The directions may be complex and not too easy to read when you actually need the hood. Being familiar with the opening instructions, donning procedures and usage is essential before you need the hood, not during the emergency.
Donning a smoke hood takes two hands, so if you don't have an autopilot or a co-pilot, trim for level flight and do your best. Opening the package may take up to 30 seconds if you stay calm and you're familiar with the package; getting the hood on and adjusted may take another 15. Blue says, "It depends on how freaked out you are and how much smoke has accumulated. If you smell a little smoke, open it up and get ready to don it. If the smoke doesn't increase, that's OK."
Blue urges consistency in placement of the hood; he Velcros it to the carpet by his seat. "I keep it in the same place every time so I can grab it without thinking about it. Include it in your preflight checklist and touch it every time."
Jonathan Elkoubi, general manager of Safer America (source for two of our test hoods, the Parat C and the COGO), says a hood should be easily stowable and retrievable in the cockpit's limited space. He noted that their sample hoods were tested with children: The average time to don a Parat-C was eight seconds and the COGO took seven to 10 seconds. The now-recalled Evac-U-8 had a response time of four to eight seconds.
And speaking of children, does it make sense to have a hood for every occupant? Our view is no. Unless you brief the occupant on using the mask -- unlikely -- helping them with it inflight is a non-starter and will distract you from you primary duty to get the airplane on the ground.
Each of the hoods we tested worked well once on -- which one you choose depends on your facial features (beards, long hair and glasses are complicating factors) and how quickly you can don it. If glasses, a beard or long hair are a consideration, avoid the COGO and go with the Parat-C or the Safe Escape.
Otherwise, we think the Parat-C is the best choice, if cost isn't a factor for you. It's easy to put on and kept the smoke at bay. But at $69.95, the Safe Escape hood is less than half the price of the Parat-C and thus represents the best value of the three, even given its donning foibles. The work-around for that is to train a little on quick donning and learn to set the straps correctly.
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