Letters to the Editor
departments
Fire Engine Color
Bloomington, Ind.:
I recently came across Ray Henry’s article entitled “What’s Visible and Safe? It’s Fire Engine Red.”
In his defense of red he makes a number of incorrect statements. For example, he cites color blindness prevalence as being “five or six out of every thousand people.” The fact is that eight out of 100 men have a color vision problem and two out of 200 cannot distinguish a good red as different from black.
Mr. Henry next states that “Lime-yellow engines can meit into most backgrounds unnoticed.” The average outdoor scene reflects 13 percent, lime-green reflects well over 60 percent and if it is fluorescent, it will reflect 200 to 400 percent. There is no way that such a brightness difference (13 percent compared to 60 to 400 percent) can “melt into most backgrounds.”
It is difficult to know whether Mr. Henry’s defense of red is based on fluorescent or standard reds. He does not draw a clear distinction between the red of maple leaves and Coast Guard buoy reds for example. Fluorescent orange is outstanding in a forest scene in the daytime, but standard fire engine red has been proven to be poorly detectable when worn by hunters in an outdoors California environment. Certainly neither standard nor fluorescent red has any increased visibility at night where reflectances are not likely to exceed 14 percent even for normal eyes.
Under the psychological value for red, Mr. Henry suggests that red inherently means danger. I would hasten to point out that cherries, tomatoes, flowers, apples, beets, etc., and lipstick are red, none of which implies danger to me.
The following remarkable statement merits a few comments: “Since red spells danger and attention more emphatically than any other color, it follows that it becomes the most recognizable color for visibility and safety.” Since one out of 12 men have a problem with either detecting red or in confusing it with other colors, it would seem that the above statement is not supported. Visibility and safety are related to one another but have no obvious relationship to red. Visibility is determined by brightness contrast more than color contrast and the yellow-green recommendation for fire equipment provides two to 20 times the brightness of non-fluorescent fire engine red.
All humans have a problem with all red paints at night. The human eye becomes insensitive to red light intensities at about one half full moon illumination levels. Red lights, of course, do not suffer this problem at night but by themselves are not easily localized. The bright yellow-green paint makes the fire truck itself visible and greatly improves the visual interpretation of its location.
Mr. Henry’s appeal to tradition is not balanced by proof that tradition is optimum. Certainly red is unique but it is also not seen by one out of 50 men and is confused by one out of 12. It fades to black as darkness comes on, it is not a safe color for hunters unless it is a special fluorescent orange-red. The idea that red means danger must be viewed against the fact that red is used everywhere in other ways. Its association with food and other good things hardly gives it the unique quality of danger in my opinion.
The fire truck issue is basically how can we make its presence and location known with the least ambiguity? That it is a fire truck is of secondary importance. The yellow-green color certainly gives a greater standout value in the everyday environment than fire engine red, and for all people—male or female, normal or color blind. Furthermore, it retains this distinctive advantage at night. With lights and sound, yellow-green is an excellent choice for fire engines.
Merrill J. Allen, O.D., Ph.D.
Professor of Optometry
Indiana University
Cavitation
South Saint Paul, Minn.:
Lieutenant Reeves, in his article “Cavitation: Warning Signs and Reasons Why It Occurs” in the October issue of Fire Engineering makes some important points. In doing so, unfortunately, he has oversimplified the subject and I feel that certain inaccuracies should be brought to your attention.
For example, the article states, “Pressure gages at sea level show a reading of 0 pounds per square inch gage (psig).” Of course, gages will show a reading of 0 at any altitude providing that they are not subjected to any pressure different from atmospheric pressure. Then, in discussing the mechanics of cavitation, the article states, “As the vapor reaches the discharge side of the pump, it is subjected to a high positive pressure which condenses the vapor back to a liquid.” Actually, the collapse of the bubbles of vapor occurs as soon as the pressure is increased sufficiently to condense the vapor, which is usually inside the impeller just beyond the leading edges of the vanes, and long before the liquid reaches the discharge side.
The most serious oversimplification is the statement, “… when (the pump) tries to pump more than it is drafting, the pressure on the discharge side is reduced and the amount of vacuum on the suction side is increased until cavitation or loss of prime occurs.” Actually, the discharge pressure will drop only if the pump capacity is reduced, and thus after cavitation occurs. Cavitation results only when the absolute pressure is reduced below the vapor pressure of the liquid. Conversely, cavitation can be avoided by any one of several changes in the pumping conditions, but the only practical way in fireground application is to deliberately reduce the pump capacity. This will decrease the value of absolute pressure at which the pump will cavitate (“required NPSH”) and at the same time will increase the absolute pressure at the pump inlet (“available NPSH”) due to the lower friction loss in the suction strainer and hose.
In discussing the possibility of judging when cavitation will occur by reading the vacuum gage, the article states, “Some of the most experienced pump operators may be able to judge by the gage, but it is a poor indication at best.” Because the absolute pressure at which cavitation will occur depends on the net pump pressure and water temperature, as well as on pump capacity, while the vacuum reading for a given absolute pressure depends on the atmospheric pressure, it is impossible to determine the vacuum at which cavitation will occur unless all of these other parameters are known. Even if they are, it is impractical to do so. The only practical way is by observing the behavior of the pump/engine combination. Then, if cavitation does occur, the discharge gates may be partially closed as suggested, in order to reduce the flow and stop the cavitation. This will increase the discharge pressure but reduce the line pressures. It is better practice to close the throttle partially to reduce the pump speed.
Compliments are due Lieutenant Reeves and Fire Engineering for bringing this subject some of the attention it deserves. I hope that my comments will be helpful.
D. F. Thomas, P.E.
Vice President
Waterous Company
In Defense of Public Education
Salem, Ore.:
I was indeed surprised and disappointed that a person of your influence and position would echo the traditional claim that fire protection and fire suppression are synonymous. A parallel can be drawn between the publication of your editorial, “NFPCA Transfer Looks Good,” and the irresponsibility of the news media when it slants the news to sell newspapers. Does a publication such as Fire Engineering need to fall prey to the self-serving needs of the fire service or should it be dedicated to the solution of the nation’s fire problem so well articulated by the National Commission on Fire Prevention and Control?
Some of your statements say it all: “Only a relatively small amount of this money went toward upgrading the fire suppression forces … A good deal of the blame for this neglect falls on the outgoing administrator who, at least in our opinion, gave low priority to the brothers-in blue … In any event, we look forward to seeing the fire (fighting) service receive a little more attention from the federal focus on the fire problem.”
You have a right to your opinion, but after all these years of emphasizing fire fighting and suppression, demonstrated by the fact that 90 to 95 per cent of all fire department budgets have been dedicated to fire suppression, you would think that we would start looking for a better way. I would think that we would look for an alternative in light of the fact that national loss statistics have not gone down and in fact are among the highest in the world.
My opinion is that Howard Tipton tried to implement an alternative fire protection system by emphasizing fire prevention, fire education and master planning as articulated in America Burning. It is also my opinion that America Burning was not written for the interests of the fire service but instead identifies that fire problem of this nation.
The NFPCA was created to solve the nation’s fire problem and not to serve in a client relationship with the fire service. So often the client group of federal agencies expect and receive benefits which do not result in solutions to the problems for which they were formed. This is what you have proposed whether knowingly or unknowingly.
I hardly think that the federal government, given the current mood of the nation, should be in the business of subsidizing local governments, whether it be providing training or providing grants to purchase the latest custom-made fire apparatus.
I feel that you were unfair in your claim that the fire administrator had a low priority for the brothers-in-blue. The fire problem was identified in America Burning. NFPCA was seeking the solution; that was Howard Tipton’s priority. In the long run, by orienting the fire service in the direction of fire prevention and public education, while not forsaking the vital role of the fire service, fire fighting, suppression forces, as you call them, will be upgraded both in their own eyes and in the eyes of the public.
The citizen’s tax revolt is telling government to be more effective and productive in the use of our financial and human resources. The national fire problem will never be solved by bigger or better fire fighting, suppression forces. The only hope is in the full utilization of the same fire fighting, suppression forces, in fire prevention and public education.
John Degnin, Jr.
Fire Chief
