From Industrial Hygiene Bulletin.
The public garage or service station presents a special problem in ventilation-that of adequately disposing of the carbon monoxide which is being constantly generated by cars undergoing repair. The extent of the carbon monoxide hazard in these service stations can only be appreciated when one considers that cars, in the process of repair are being constantly started and stopped, and that in the course of the testing process, the air-gasoline ration in the carborater may at times be very low. The exhaust from a car which is being run under these conditions has a far larger percentage of carbon monoxide than has the exhaust from a car which is being normally operated.
The further fact that the density of carbon monoxide is practically that of air (0.9678) prevents it either from rising to the ceiling of the workroom, or from settling to the floor in the way that carbon dioxide to do. Because the cars are often in motion when they are being tested any attempt to remove the gas at its source becomes a very difficult task indeed. Air tests recently conducted by Dr. Salls, chemical engineer of the Bureau of Industrial Hygiene, revealed the fact that two feet in back of cars which were actively exhausting, the concentration of carbon monoxide in the air was from seven to eleven parts of carbon monoxide per 10,000 parts of air.
The public Health Committee of the New York Academy of Medicine reports the results of the analyses of the exhaust gases of 23 cars by volume, as follows.
On Level Grade Ascending 3 percent Grade.
Per Cent. Per Cent.
Carbon dioxide 8.6 7.6
Oxygen 2.3 1.3
Carbon monoxide 6.3 6.4
Methane 0.9 0.6
Hydrogen 3.0 2.9
Nitrogen 78.6 79.2.
During the warm weather, it must be remembered that a unit weight of air will occupy a considerably greater volume than when it is cold, with the result that the same carburettor adjustment will suck in a smaller amount of oxygen, and the percentage of carbon monoxide in the exhaust gas will in consequence be correspondingly higher.
An investigation by the Bureau of Industrial Hygiene of 31 service stations brought to light the fact that 24, or 77.4 per cent., showed the presence of carbon monoxide in the air, and 17, or 54.8 per cent., showed a concentration of this gas which in excess of the 0.1 per cent. regarded by authorities as the danger limit. Of the 42 workers examined at the time, 29, or 69 per cent., showed definite evidence of carbon monoxide in their blood, and a number presented clinical symptoms of carbon monoxide poisoning. In subsequent examinations the carbon monoxide was found to range from 2.3 per cent. t0 40 per cent. saturation.
The oxygen content of the blood of these men ranged from 2.4 volumes per cent. to 10.8 volumes per cent. the normal being approximately 19 volumes per cent. The average oxygen content was found to be 5.8 volumes per cent., or only little more than one-fourth the normal oxygen content of the blood. This very striking anoxemia is a serious menace to health, since it is indicative of marked reduction in the amount of oxygen which the blood can carry to nourish the tissues of the body.
Of all the clinical manifestations of prolonged exposure to carbon monoxide poisoning exhibited by these men, it was the prevalence of the carbon monoxide headache which had above all else hazard, and the urgent need for doing something drastic about it. The carbon monoxide headache is a most intense pounding headache which may come on hours after exposure to the gas has ceased, and which is of very long duration. Indeed, it may continue for hours after all carbon monoxide has been removed from the blood, by prolonged exposure of the individual to fresh air.
This headache is in itself responsible for more loss of time on the part of workers exposed to even relatively low concentrations of carbon monoxide than any other one or group of symptoms complained of. Dizziness, smarting of the eyes, nausea, drowsiness and lack of proper muscular coordination were all complained of to greater or less degree by the men examined. But these were not usually the cause for laying off work, although they undoubtedly seriously impaired efficiency, and predisposed to accident. The carbon monoxide headache, however, is the usual and chief cause for loss of time.
Various methods are being with a view to ridding their service industry at the present time with a view to ridding their service stations of the carbon monoxide hazard. The installation of elaborate forced draft ventilating systems, capable of keeping the air fresh at all times appears to be far too expensive to be practicable in most instances. Instead, therefore, managers of service stations are becoming interested in the use of various chemical substances now on sale, which if sprayed, or otherwise introduced into the air are supposed to “improve the condition of the air.” Just how this is to be accomplished is frequently very vague both in the minds of the manufacturers of these products and those who purchase them for their service stations.
The Bureau of Industrial Hygiene has been called upon by some of the more intelligent service station managers-particularly those having a large number of service stations to provide for-for a disinterested opinion as to the efficacy of these measures. One of the chemical substances on the market is essentially a combination of chlorine and formaldehyde, which is to be sprayed into the workroom.
This is now under investigation by the bureau. The other chemical substance which is making considerable headway in garages and service stations is ozone, chemically designated as O3. Ozone is generated in the room by means of one or more ozone generators of varying sizes depending upon the size of the service station.
Manufacturers of these ozone machines are not all agreed as to its effect either upon the air of the workroom or upon the men exposed. One manufacturer in his sales literature points out that ozone or O3 is broken down into O2 plus O, and that the one atom of nascent oxygen combines with the carbon monoxide in the air to form carbon dioxide which in the concentration produced would be quite harmless (O+CO=CO2). In this contention he is not supported either by the other manufacturers of these machines or by experimental evidence. That under conditions prevalent in service stations, this reaction does not occur to any appreciable extent whatever is well established scientifically. This conclusion had further been independently arrived at and confirmed by experimental work conducted by the Bureau of Industrial Hygiene.
The fact that many of the men working in service stations where these machines have been installed “on approval” appear to be genuinely enthusiastic about them, however, and claim that they feel so much better and have fewer or no headaches since their installation has caused the Bureau of Industrial Hygiene to investigated the matter further. It has been our experience as a result of an examination of a considerable number of these men that exposure to carbon monoxide seems to make them hyper- suggestible.
The question immediately arose, therefore, whether perhaps the sole effect of these machines was psychological. On the other hand, the men continue to insist that they really do have fewer headaches, and some claim to have none at all any more since the ozone machines have been installed. The carbon monoxide headache is too real and too intense to be disposed of purely by suggestion.
Despite the fact, therefore, that the use of ozone in ventilation has no scientific standing at the present time, and despite the fact Bureau of Industrial Hygiene feels that the question of the use of ozone in service stations requires careful study. If the effect of exposure to this gas is entirely psychological, this should be established very definitely. On the other hand, it is felt that the direct effect of exposure to ozone upon the physiological and chemical function of the body is not entirely understood at the present time, and that possibly further study along these lines might bring to light an explanation of the popularity of these machines with workers who are exposed to the carbon monoxide hazard in garages and service stations.
In the investigation now in progress, careful physical examinations are being made and blood tests taken. The question of the physiological effects of exposure to ozone are being considered from several angles, most important of which perhaps are the following:.
1. Does exposure to ozone tend to cause a rise in the haemoglobin of the blood, thereby assisting the body in maintaining a normal oxygen carrying capacity despite the fact that some of the haemoglobin is tied up with carbon monoxide and so cannot adequately fulfil its normal oxygen carrying function? Blood tests made by the bureau recently of workers exposed to carbon monoxide in service stations seemed to show that the normal reaction of the blood to such exposure is first to cause a compensatory increase in the haemoglobin, apparently for this very purpose. This is then followed by considerable destruction both of red cells and haemoglobin.
2. Does the presence of ozone in the air tend to increase the partial pressure of the oxygen in the alveolar air, thus making it more available to the tissues? Stadie has advanced the theory, as a result of animal experimentation, that the primary effect of carbon monoxide inhalation is its profound alteration of the normal oxygen dissociation curve, rather than the mere loss of functioning haemoglobin.
This alteration, he believes, is caused by the fact that due to the presence of carbon monoxide in the alveolar air, the partial pressure of oxygen is markedly reduced, so that the same volume of oxygen if carried in the capillaries would still not be equally available to the tissues. If ozone, in quantities produced by the ozone machines now in use, can materially alter the partial pressure of oxygen in the alveolar air, this might offer an explanation for their popularity with the men.
There are still other questions along these general lines which the Bureau of Industrial Hygiene is now working on.
with the cooperation of the Cornell Research Laboratories located at Nursery and Childs Hospital, and the manufacturers of cone of the ozone machines now on the market, an “Ozonator” has been installed in the hospital. Experimental work in now in progress there both for the purpose of getting a normal control series, and for the purpose of conducting further and more intensive investigations of the general physiological effects of exposure to ozone.
A report of the findings will be issued for the information of the automobile industry and others interested as soon as this date has been assembled.