To the editor: First, thank you for a fine magazine. I look forward to receiving every issue and I enjoy the full range of topics and articles. I have to say than when I read David Lynn’s article in a recent issue (“A hookah dive system,” November/December 2012, Issue 206) that I was quite taken aback by the presentation of using nonstandard equipment for breathing compressed air underwater. The topic and content of the article was especially surprising to me since I normally enjoy his thoughtful and thrifty solutions to everyday boat issues from mast climbing to knocking together an emergency diesel day tank.
As a diving professional and sailor, both for more than 30 years, I feel compelled to suggest that this article could foster risky behavior and life threatening conditions.
No general purpose or “shop” compressor company that I have been able to find recommends that their products be used for purposes of breathing air either at the surface or underwater. You can simply do a quick Internet search for “shop compressor manual” and most often the very first warning is to NOT use the unit for breathing air. It is more than just legalese.
Second, Mr. Lynn surfaces very incomplete information about what contaminates might be found in compressed air from shop compressors. In his statement that he connected a “standard pneumatic air filter and water trap to the compressor with quick disconnect fittings to prevent rust or dirt particles from being inhaled,” he completely misses the most important potential toxins. I would refer you again to any average shop compressor manual that warns not only of particle contaminates, but of the real possibility of carbon monoxide and oil contamination as well. Both are not only fast-acting toxins, but their dangerous effects are increased with the increasing pressure of depth underwater. Look up exogenous lipoid pneumonia to learn more about oil in breathing mixtures and give yourself a refresher on Henry’s Law to better grasp the hazards of increasing toxicity of a gas under pressure. Breathing gas quality under pressure is so vital that it is regulated by OSHA and the Compressed Gas Association in the USA, whose guidelines are adopted by all the major scuba training agencies and equipment manufacturers.
Third, beneath Mr. Lynn’s own selection of equipment lies even further risk. In order to successfully deliver enough air at a prescribed depth, a regulator must be balanced. Otherwise, in an unbalanced scenario the ambient pressure at depth eventually overcomes the air delivery pressure and airflow ceases. Depending on the actual temperature, delivery pressure and reliability, this could happen in a quite shallow environment. Additionally, the photograph of the hose connection on page 42 shows what looks like a corroded and re-used hose clamp on a lightweight water hose and a quick disconnect of unknown material and pressure capacity. A failure of any of the three could cause, at the surface, a whipping hose that could lead to significant injury as I know from my own personal experience, and underwater would abruptly terminate air delivery. No person familiar with breathing air systems would ever approve of or use such a rig as shown here.
Fourth, while Mr. Lynn is correct in his assertion that scuba training is not a requirement, it is strongly suggested for good reason: ignorance kills. Mr Lynn includes no discussion of the real and present dangers of arterial gas embolism. In shallow water, this is the most acutely dangerous of all scuba diving maladies and it only occurs when using compressed gas underwater, which is of course the theme of this article. Even if Mr. Lynn’s magnificent diving machine does not kill him, a lack of knowledge of the golden rule of scuba diving can kill him in less than one meter of water while he is only at propeller depth!
In a pinch would it do to unwrap a prop? Probably, but learning a little more about breath hold diving would be much faster, safer and more practical.
—Todd Smith has 30 years diving experience including salvage, police, research, technical, commercial and recreational. Smith is a Technical Diving Instructor Trainer and PADI Instructor Trainer with diving experience on six continents and all the world’s major oceans. After sailing and diving experiences in New England, the Great Lakes and the Caribbean, Smith and his wife Capt. Anita are finishing up a refit of their 36-foot Cartwright Cutter and plan a circumnavigation.
David Lynn responds: Thanks, Todd, for such an insightful, well thought out response to my article. You are obviously quite knowledgeable on the subject, and I appreciate your feedback.
Your first concern relates to the use of an inexpensive, commercial oil-free air compressor to provide breathing air. My compressor manual has two pages of warnings, including the risk of injury from dropping the device on one’s foot, the risk of electrical danger if you use an inadequate extension cord, and the fact that there are hot surfaces present. There is also a warning about using it for breathing applications, and warns that there are risks of breathing particulate matter, i.e. rust or dirt from the incoming air or from within the tank, and the possibility of breathing carbon monoxide or other toxins.
Assuming the particulate matter was filtered out, my thinking was that since an electric motor driven, oil-free compressor does not generate carbon monoxide or other toxins, the manufacturer’s concern was that there is a possibility of the compressor drawing in bad air and passing it on to the diver. In our litigious society, manufacturers need to protect themselves from lawsuits when someone drops it on their foot or breathes the compressed air while operating the compressor downwind of a gasoline engine. I was certainly not intending to be cavalier and I hope I am not overly naïve on the subject, but I have used my hookah system several times and have had no ill effects.
Your point regarding the use of an unbalanced regulator is one I disagree with. An unbalanced regulator working with the lower pressures of a hookah compressor will indeed stop functioning at some depth. I don’t know what this depth is, but I do know my regulator works well at depths up to about 15 feet. I do mention in the article that I don’t know whether it will function in deeper water. A more expensive balanced regulator would work to greater depths, but this is an unnecessary expense in my intended application.
As to the fittings, perhaps the photo wasn’t clear enough. The hose clamp is a new stainless clamp. I certainly did not reuse a corroded and rusty hose clamp to attach the quick disconnect fitting. All the fittings were standard brass pneumatic fittings rated at 150 PSI or more. The hose is rated to 250 PSI. Since the compressor has a maximum output pressure of 90 PSI, this seemed like a reasonable margin of error. The fittings are brass and should be rinsed thoroughly after immersion in saltwater, as mentioned in the article.
Todd’s concern with the use of a hookah by someone untrained is well taken. As a diver ascends and the gases in the lungs expand, the risk of lung damage and/or arterial gas embolism is a real danger, and one that anyone who has taken a diving course is well aware of. You must ascend slowly, breathing normally or exhaling as you rise. In the article, I do recommend taking dive training before using a hookah. Todd is correct — ignorance can be deadly.