Personal Respiratory Protective Devices
Huh? You mean smoke hoods? Aren't they just for paranoid white-knuckle flyers and airline safety gloom-and-doomsters like Mary Schiavo and Ralph Nader? That's what AVweb's Mike Busch thought, too, until he looked into the subject. Now he doesn't leave home without one, and explains why.
by Mike Busch
This article originally appeared in AVweb, the Internet's aviation magazine and news service, and is reprinted here by permission.
Click here to jump to Doc Blue's Smoke Hood recommendations.
I've been flying for 35 years, but I must confess that the first time I ever became conscious of personal respiratory protective devices (commonly known as smoke hoods) was in mid-1997 when I read about them in Mary Schiavo's book Flying Blind, Flying Safe. I'm sure you recall Ms. Schiavo as the former DOT Inspector General (and former beauty queen) who quit her job in 1996 in a blaze of anti-FAA, anti-airline TV sound bites, and then released a book about airline safety calculated to scare the hell out of the public and to exploit their fear about the ValuJet 592 and TWA 800 tragedies. She hawked her book mercilessly on the TV talk-show circuit, and wound up making the cover of Time magazine. Frankly, I found Schiavo's fast-and-loose treatment of the facts and her safety-at-any-price philosophy to be abhorrent. Even today, when she appears on TV as a so-called aviation safety expert, I involuntarily reach for the remote. In fairness, I have to give Mary Schiavo credit for first putting smoke hoods on my radar screen. However, since I hated her book and disagreed with almost everything she said and every position she took, I wasn't exactly galvanized into action to run out and buy some smoke hoods for my Cessna 310. I suppose that Schiavo's enthusiastic endorsement of smoke hoods was the kiss of death for me. In any case, I didn't pursue the matter.
Taking a second look
My interest in the devices was rekindled (so to speak) more than a year later when I undertook an evaluation of carbon monoxide detectors for inflight use. My article was published by AVweb and generated a great deal of reader interest and feedback. Numerous readers who bought a digital CO detector at my recommendation wrote to ask "What should I do if the thing goes off in flight?" My answer was "Get on the ground, fast, but that was not a terribly satisfying answer. I knew from my investigations into the physiology of CO poisoning that high concentrations of CO (500 PPM or more, as might be experienced in the event of a major exhaust-system failure or a cabin fire) could easily incapacitate a pilot before he or she could land. My interest in smoke hoods was also heightened by the Swissair 111 crash, which may very well have involved a cockpit fire and crew incapacitation according to preliminary indications. While I was prepared to write off ValuJet 592 as a freak occurrence caused by carriage of illegal hazmat cargo, the Swissair crash had "there but for the grace of God" written all over it. If that sort of thing could happen in a sophisticated wide-body airliner bristling with fire detection and suppression gear, what about my Cessna 310? If my cabin filled with CO or smoke or toxic gases in flight, what's the chance I could maintain control long enough to get down in one piece? Upon further investigation, I discovered that even if you do manage to land the aircraft, there's a significant possibility of dying on the ground from smoke inhalation before you can get out of the airplane. While this is a particularly serious problem with transport aircraft, it often occurs in general aviation mishaps as well.
The accident record
As I often do when thinking about safety issues, I took a look at the NTSB database to get some feeling for how often smoke inhalation was a factor in aircraft accidents, both airline and general aviation. (Isn't the Internet great?) It quickly became obvious to me that the availability of protective breathing devices would have been decisive in quite a few high-profile air carrier accidents:
In 1973, a Boeing 707 landed in Paris, France, eight minutes after a fire broke out in a lavatory. 124 passengers and crew died from breathing toxic smoke and fumes. Only two people survived.
On June 2, 1983, an Air Canada DC-9 en route from Dallas/Fort Worth to Toronto declared an emergency after fire broke out in a lavatory. The captain made an emergency landing in Cincinnati, Ohio, and the cabin crew commenced evacuation, but a minute after the exits were opened, a flash fire enveloped the interior of the aircraft. Of the 46 aboard, 23 were overcome by smoke and fumes and died before they could get out.
On August 22, 1985, the captain of a British Airtours Boeing 737 rejected a takeoff from Manchester, England. The left engine caught fire and the cabin filled with thick black smoke. The cabin crew attempted to evacuate the aircraft, but were hampered by utter panic among the choking passengers who could not see or breathe. 82 survived, but 55 died -- 48 of them from smoke inhalation, according to a House of Commons report.
On July 19, 1989, a United Airlines DC-10 crash-landed at Sioux City, Iowa, after a catastrophic failure of the tail-mounted #2 engine caused a complete loss of all three hydraulic systems that powered the flight controls, and rendered the aircraft nearly uncontrollable. Of the 296 aboard, 111 people died, 37 of them from smoke inhalation.
On December 3, 1990, a Northwest Airlines DC-9 collided with a Northwest Airlines 727 during a runway-incursion accident in heavy fog at Detroit Metro. The DC-9 caught fire and eight passengers died, seven of them from smoke inhalation.
On February 1, 1991, a landing USAir Boeing 737 collided with a position-and-hold Skywest Metroliner at Los Angeles International Airport as the result of an ATC operational error. Of the 34 fatalities aboard the USAir jet, 22 died from breathing toxic smoke and fumes.
David Koch's ordeal
One of the survivors of the 1991 USAir collision at LAX was David H. Koch of Wichita, Kansas. Koch is a well-known philanthropist, libertarian activist, and executive of oil and gas producer Koch Industries, and is estimated by Forbes to have a personal net worth of $1.8 billion. Koch documented his experience rather vividly in Recollections of My Survival of an Airplane Crash. Here's an excerpt:
The cabin lights immediately went out and people began to scream hysterically and rush down the aisle toward the rear of the plane. A few seconds later, the interior of the plane began to fill with intense, heavy black smoke, which was extraordinarily painful to breathe and very toxic. I reached for my suit jacket, but could not find it. My thought was to use it as a face mask to protect my lungs from the smoke. I was on my hands and knees attempting to crawl down the aisle toward the rear of the plane. Several people stampeded over me. It quickly became pitch black in the cabin from the heavy smoke, in spite of the bright light from the fire on the left side of the plane. I could only make out the vague outlines of people directly in front of me. As I moved down the aisle, I encountered a mob of fighting, frenzied people jamming the aisle. At that point, I stood up on my feet, choking heavily from the smoke, and walked back toward the first class section. My state of mind was objective about the condition I was in. I had a real sense of curiosity about what it would be like to die. ... To my astonishment, I detected an opening between the [galley service] door and its frame on the right side of about several inches in width. It was possible to see light on the other side. By this time, I was feeling very faint and I later guessed I only had about 15 to 30 seconds of consciousness left. Every breath caused me to convulse and was extremely painful. I put my fingers in the opening and pulled. The door moved somewhat, which enabled me to put my head out and take a deep breath of fresh air. A tremendous feeling of strength came over me and I felt like Superman. I revived somewhat. With this added energy, I pulled the door more and it moved to the left a couple of feet. This permitted me to step into the doorway and jump to the ground below. I crawled and stumbled away from the plane and ran about 30 yards before stopping. My lungs hurt terribly and I coughed and choked badly for about five minutes before I could breathe normally again.
Not surprisingly, Koch has become a fervent believer in protective breathing devices. He is convinced that most of the victims of the USAir crash would have survived if they'd had protective breathing devices available to them. "I carry one in my briefcase now," he says.
General aviation, too
Although occupants of general aviation aircraft are generally a lot closer to the exit, the G.A. accident record is full of deaths caused by breathing toxic smoke and fumes. One of the most famous occurred on August 2, 1979, when New York Yankees catcher and batting champ Thurman Munson was killed while practicing takeoffs and landings at Canton, Ohio, in his newly-acquired Cessna Citation. A low-time pilot, Munson undershot the runway on one landing attempt, and the plane caught fire in the ensuing crash landing. Munson's passengers escaped unharmed, but Munson didn't. The cause of his death was determined to be smoke inhalation. Here are a few other G.A. accidents of more recent vintage:
On May 22, 1993, a Beech 18 nosed over during a landing in windy conditions at North Branch, Minn., due to the pilot's excessive use of brakes. The aircraft burned. The passenger escaped unharmed, but the pilot died of smoke inhalation and carbon monoxide poisoning. Toxicology tests at autopsy showed the pilot had 58% carboxyhemoglobin saturation and 1.1 mg/L cyanide in his blood.
On October 6, 1993, a Piper Aztec with a CFI and multiengine student aboard collided with trees while in the traffic pattern at East Hampton, N.Y. The aircraft was destroyed by post-impact fire, and both pilots were fatally injured. An autopsy listed the cause of death as "smoke inhalation and thermal injuries."
On January 12, 1995, collided with the ground and burst into flames as the pilot attempted an emergency landing two miles south of the airport at Augusta, Ga., after an engine failure. The four people aboard the IFR flight were fatally injured. A postmortem exam ruled the cause of death for the pilot and passengers as smoke inhalation, with a 28% level of carboxyhemoglobin and 0.29 mg/L of cyanide in the pilot's blood.
On August 11, 1995, a Piper Cherokee 140 impacted trees one minute after takeoff from Pulaski, Tenn., crashed inverted, and burned. The pilot and passenger died from smoke inhalation and burns. The autopsy found high levels of CO in the blood of both occupants. A bystander who attempted to rescue them stated that both were alive and he attempted to kick in a side window but was unable to do so before the occupants were overcome.
On January 15, 1996, a homebuilt KR-2 crashed and burned during high-speed taxi tests at Denver's Front Range airport. The pilot died from inhalation of smoke containing lethal levels of cyanide. The aircraft was constructed of wood, foam and fiberglass, and the foam produces cyanide when exposed to extreme heat associated with combustion.
The bottom line seems to be that if you wind up inside a burning airplane, you're very likely to be overcome by suffocation and CO poisoning -- literally "drowning in a sea of smoke" -- rather than burning to death. I suppose that's good news, in a morbid sort of way. However, if you had an inexpensive respiratory protective device within reach, you'd be far more likely to find a way to safety or to be rescued.
Not just an aviation problem
Fire protection has become a multibillion-dollar industry. Today, virtually every home, hotel room and office has a smoke detector, and CO detectors are rapidly becoming more commonplace. Hotels and commercial buildings are equipped with sprinkler systems. More and more buildings are being constructed with fire-retardant materials. Yet 60,000 people will be seriously injured in fires this year, and 10,000 will die. Approximately 80% of those deaths will be caused by inhalation of toxic smoke and fumes, not by burns. It is smoke, not flame or heat, that kills the vast majority of fire victims. Smoke is laden with a host of lethal toxins, including:
- Sulphur Dioxide
- Hydrogen Chloride
- Hydrogen Cyanide
- Carbon Monoxide
Carbon monoxide (CO) is the major toxin responsible for most fire-related fatalities.It's often called "the silent killer" because it's odorless, colorless, and incredibly deadly. CO is present in virtually all fires, and is lethal in concentrations as low as 0.5% (500 PPM) and incapacitating in even lower concentrations. The psychology of smoke inhalation is also an important factor. Engulfed in smoke, it's difficult to see, breathe or communicate. People exposed to smoke quickly lose the clear-headedness, mobility and orientation that are vital to a safe escape. Panic-stricken victims often hyperventilate, gulping in massive amounts of toxic smoke and fumes and greatly hastening their demise. Shockingly, the time interval from detection to death can be as little as 60 seconds. A smoke alarm or CO detector will alert you to the presence of smoke or toxic gas, but it will not provide a passage to safety. If you're more than 30 seconds or so away from an exit, you may not make it without some sort of breathing protection.
Will a smoke hood really help?
When I first heard about smoke hoods, I visualized something akin to a Ziploc freezer bag that goes over your head. Frankly, the idea seemed pretty silly. How long could you breathe with a plastic bag over your head? How long would it take to fog up inside so you couldn't see? Turns out that most smoke hoods do indeed have a transparent bag that goes over your head, although the good ones are made not from plastic but from DuPont Kapton that resists high heat and transient flame. The hoods typically have some arrangement for sealing snugly around your neck: drawstrings, elastic, or a neoprene collar. The purpose is primarily to protect your eyes from smoke, and secondarily to protect your face, head and neck from heat. But the most important part of a personal respiratory protective device isn't the hood. It's the filtration system that filters the air you breathe and prevents toxic gases, fumes and particulates from reaching your lungs. It's in this area that personal respiratory protective devices offered by various vendors differ most significantly. Virtually all smoke hoods incorporate an activated charcoal filter designed to filter out corrosive fumes such as chlorine and ammonia, acid gases such as hydrogen chloride and hydrogen sulfide, and various hydrocarbons, alcohols, and other solvents. Many also include some sort of filter screen designed to block particulate matter. As mentioned earlier, however, the toxin responsible for most fire-related fatalities is none of these. It's colorless, odorless carbon monoxide. Unfortunately, CO cannot be filtered out by activated charcoal or anything else. But, it can be converted to relatively harmless CO2 through a catalytic process. The best smoke hoods include such a "catalytic converter" that will protect you from CO until the catalyst becomes contaminated. Surprisingly, only two of the five smoke hoods I looked at offered meaningful CO protection. Frankly, I cannot imagine buying a smoke hood that doesn't. Other key attributes of a good smoke hood are good visibility, compact size, comfort, and reasonable cost. Virtually all of the units come in sealed packages (to protect the filter from contamination prior to use), and have a shelf life of five years
Now I know that it's difficult to get excited about a product like a smoke hood. After all, with any luck, it's something you'll never actually have occasion to use. If you buy one, odds are you'll keep it for its full five-year shelf life without ever breaking the seal. On the other hand, for roughly a dollar a month, it's a modest price to pay for peace of mind in airplanes, hotel rooms, and other places where egress might take longer than the time you have without a protective device. It's some of the cheapest life insurance you'll ever find.
Which smoke hood to buy?
(This section has been updated with current models of smoke hoods by Dr. Brent Blue. Mike’s most highly recommended hoods are no longer manufacturered)
Aeromedix has evaluated and sells only four smoke hoods that are available on the market based on the quality of airfiltration, donning ease, and cost. Two of the four models are highly recommended. Two fulfill basic requirements of airfiltration but cost and hood design put them below my favorites.
The best bang for the buck are the ASE30 and ASE60 smoke hoods. They filter all the key contaminates in smoke and have an hood with heat (mainly ash and spark in this situation) and face plate. The only difference between the 30 and 60 is the model represents the number of minutes the hoods are tested to provide protection. The units are packed in rectangular cubes which fit nicely in to the cockpit, flightbag and briefcase.
The Dover is the ultimate in protection from smoke. It is battery operated which means that air is filtered by its internal compressor to fill the hood with fresh air. No mouth piece is required and the blower keeps the face screen clear. This is why the Dover is standard equipment in the Pentagon and is located in multiple areas on the walls of that building.
However, the Dover is relatively large and expensive but if you want the best, the ILC Dover CBRN is the ultimate in protection. If you want anything better than this, you would have to use a firefighter’s tank system.
The Plus 15 unit’s main advantage is it small packaged size. Its’ price makes it less advantageous than the ASE30 & 60. It has good filtering characteristics but its hood offers less protection than the ASE as well.
The iEvac has a good filtration system and face mask but the cost makes it less advantageous than the SAE models. Its facemask is smaller than the Plus 15.
Bottom line recommendation for me is the ASE30 & 60 for aircraft and travel use. For workers in high rise buildings and home use, I would recommend the Dover CBRN. - Brent Blue MD
One last word from Mike Busch: You CAN take it with you
One evening as I was researching this report, I happened to be viewing a short videotape that illustrated how to don a smoke hood. My wife wandered by at that moment, and the video caught her eye.
As the video ended, I explained to Jan that I was thinking about buying a couple of smoke hoods for the airplane.
"What do they cost?" she asked.
"About $70 apiece," I replied.
"Would you please order two of them for me?"
I'd been thinking about the devices strictly in an aviation context, and I knew that Jan wasn't exactly a frequent flyer.
"I want one to carry in my purse whenever I stay in a hotel," she explained, "especially a high-rise hotel like the ones we stay at when we go to Las Vegas.The thought of a hotel fire has always terrified me. I'd like another one to give to my mom. She keeps all the doors to her house dead-bolted, and I'm afraid that if she ever had a fire, she'd pass out on the floor before she could unlock a door and get out."
It took me about a millisecond to realize that Jan was exactly right. A smoke hood is not something that should be left in the airplane. What if you have to escape a fire at home, in your office or hotel room? What about when you're on an airliner, bus, train, cruise ship, or elevator? If you buy one, you really ought to carry it in your briefcase, purse, flight case or totebag and keep it handy at all times. Why not? It's certainly small and lightweight enough.