Reprinted from the ACJ - July, 1995
"What's that smell!?" I said that the other day as I walked into the plant lunchroom. I was greeted by a paper cup bouncing off of my head and a less than gracious explanation that it was a co-worker's lunch being heated in the microwave.
The human nose can detect on the order of 10,000 individual odors. This may seem like an impressive number until you learn that our olfactory sense (smell) is hundreds of times less sensitive than that of a dog. So, when you blame a nasty odor on the dog, you may be fooling your companions but not Fido. He knows where the source is.
Even with our dull sense of smell we can pick up odors at as little as 1 ppb (part per billion), while others go unnoticed at one or two percent. Our ability to discern smells also varies by individual. At an EPA conference, a sample bottle was passed around. Twenty-five percent of the folks who smelled it liked the smell, 25 percent thought the smell offensive, and the remaining 50 percent concluded that the first half of the group sucked up all the smell, since they sensed no odor at all.
What does all this tell us? That our noses may not be a practical method of chemical identification. In actuality, using your nose around the shop, and at home, could be dangerous. We mentioned earlier that the concentration of specific smells affect our ability to detect them. This concentration level at which we can notice a smell is called an "odor threshold." Below the odor threshold the chemical is still attacking our nose, throat and lungs, but we don't detect it. If the chemical is absorbed into the body by an inhalation route of entry, then we may indeed be unwittingly poisoning ourselves.
The odor threshold varies for each chemical just as the level that adversely affects our health does. This wide variation in smells and health effects can be demonstrated by a comparison of several chemicals that we, as radiator folks and homeowners, know and love.
Natural gas is approximately 95 percent methane. Methane is completely odorless. We could suffocate in a room full of pure methane and never know what hit us. Lucky for us, the gas company had our best interests in mind when it decided to add methyl mercaptan to natural gas. Even at only a few parts per million, this chemical gives the gas its characteristic smell. Without it, a gas leak could harm us long before we knew anything was wrong.
On the flip side, or in the other nostril as the case may be, is hydrochloric acid (HCl). The sharp, pungent odor associated with muriatic acid is detectable, and unbearable for most folks, well below the level associated with acute adverse health effects. It would be very hard to breathe acutely dangerous HCl fumes for very long. Thus, our nose protects us against the acid fumes.
As with any piece of safety or protective equipment, maintenance is very important. We must take care of our proboscis if we want it to take care of us. It is possible to become insensitive or "used to" a smell and lose our ability to detect it as we should. Repeated exposures may clog up or wear out the receptors in our nasal passages. So be careful to wear the proper respirator and use adequate ventilation around the shop. Also get out in the fresh air periodically during the day.
Of course, for you folks in the big city, fresh air is a relative term. I made my home in Wisconsin for many years and, contrary to popular belief, we raised no dairy cows in the backyard of my folks' house on the outskirts of Madison. But quite often my travels would take me to a friend's farm. Being a city boy, I would entertain the farmers endlessly by wrinkling up my nose, coughing and choking over the overwhelming smells that emanated from the fields, barns and the sodbusters themselves. They would always say the same thing: "I don't smell nothing." Their noses had grown accustomed to the earthy smell that they equate with money.
Some poor souls take this one step further in that they have no sense of smell at all. Approximately 2 to 4 million people in America suffer from "anosmia," or the loss of the ability to sense smells. This can be caused by excessive exposure to chemicals. So again, if you don't have to smell it, don't. Never place your nose directly above a chemical or a bottle of some unknown substance to identify it. This can be dangerous and possibly life threatening.
If taking a whiff of something is necessary, hold the bottle away from your face and gently sweep some of the fumes toward your nose with your hand. Then sniff slowly and don't take a deep breath. If the odor threshold is low enough you will be able to smell it without causing harm to your mucous membranes. This is called the waft method. If your refrigerator looks like mine this is a much better method for checking if the milk has gone bad than discovering it with your first mouthful.
As we go through our daily routines, we are constantly bombarded by smells, some pleasant and others not so pleasant. By taking precautions such as wearing respirators and maintaining good ventilation when chemical fumes warrant it, and by being careful when sampling the aroma of something we are not sure of, we can be assured of enjoying nature's fragrance for many years.
One more helpful hint: If your spouse or co-workers read this, be discreet when using the waft method to identify whatever it is in their lunch dish.
The above article was written by David M. Brown, Chief Engineer of Johnson Manufacturing Company, Inc. and is published by JOHNSON with the expressed approval of the National Automotive Radiator Service Association and the Automotive Cooling Journal. Other reproduction or distribution of this information is forbidden without the written consent of JOHNSON and NARSA/ACJ. All rights reserved.
JOHNSON MANUFACTURING COMPANY
114 Lost Grove Road / PO Box 96 / Princeton, Iowa 52768-0096
Phone 563-289-5123 or Fax 563-289-3825