Laboratory Safety Information
Keynote address, 48th NEACT Summer Conference at the University of Main, Orono, Maine on August 18-22, 1986
Each of us has heard about some other teacher's serious accident to their student but unless it has happened to us, we are inclined to maybe pat ourselves on the back (while crossing our fingers) properly thankful that it didn't happen to one of our students and hoping that it never will. In these remarks, I'd like to make that hope a little more secure, a bit less uncertain. For those among you who have had a serious accident, I'd like to make it less likely that there will be another one.
So to begin. I'll ask for a show of hands: How many here have every had a close call? All of us have had at least one of these, including me. The main point I want to make is that a close call is a serious accident announcing in advance that it is coming, sooner or later -- unless you, and I, take corrective steps. Let's look at some statistics for accidents in general. These statistics are summarized in what is called the "Heinrick accident triangle." At the base of the triangle we have 100,000 hazards, or unsafe conditions. Statistically, these 100,000 unsafe conditions will cause 10,000 close calls. Saying it differently, if you had, say, three close calls last year in your lab teaching, you had thirty unsafe conditions. On the basis of 100,000 unsafe conditions, there will be 1000 recordable accidents, perhaps a burn from hot glass tubing or a spill that caused someone to slip and fall with a resulting broken arm, and so on. Turning this around, if you had three accidents last year that were serious enough to be reported, you also had 300 unsafe conditions that you did not know about and therefore could not correct, according to the statistics. The Heinrick triangle goes further. One accident that disables the victim signifies 1000 different unsafe conditions that have not been corrected. It is sobering to note that according to the statistics, a mere 30,000 unsafe unknown hazards will eventually cause one fatalist, if you or I have had one simple scratched student, which statistically signifies a mere close call, that incident strongly suggests also that there are ten hazards present that are not yet known to you or to me. But, one of those ten could be the cause of a fatality, not a mere scratch, next week or next month.
I agree that this is an extreme scenario: also emphasize that it its not implausible. The concept is straightforward. All accidents are caused. Every accident and every close call represents a large number of other causes that are unknown, unrecognized. Our task is to discover and eliminate every one of these unknowns to the extent that is possible. For this task, the principles of chemical safety will be helpful.
I. The Principles of Chemical Safety
The essence of chemical safety is comprised in four principles, each with a corollary and examples.
II. Chemical Hazards, Precautionary Measures, Emergency Procedures
The hazards presented by any chemical depend upon the properties of that chemical. Since each different chemical is different from all others because it has properties that are different, it follow s that each chemical presents different hazards. To use a chemical properly, we must know the hazards of that chemical, the appropriate precautionary measures that reduce the the probability of harm from those hazards, and the necessary emergency measures (should our precautions fail) that also depend upon the hazards. Stated in these terms, the requirements are formidable. How can I know that much about each of the many chemicals my students will use in the lab -- to say nothing of teaching all this to the students themselves?
Fortunately, there is a practical answer. Chemicals present only four classes of chemical hazards and a fifth, physical, hazard in some instances. Although one chemical may indeed be more toxic say, than another, the precautions and emergency treatment depend principally upon the toxicity, not the degree of toxicity. The four chemical hazards are flammability, corrosivity, toxicity, and reactivity. IN what follows we will look at each separately and at physical hazards as will. Keep in mind that any single chemical may simultaneously present more than one of any of these five hazards.
A flammable chemical (obviously) will burn. Other terms that convey the same hazard potential information include"extremely flammable" and "combustible." Keep in mind that the vapors of flammables, if ignited when mixed with air in suitable proportions (ranging from 1%to more than 50% (by volume) in some cases) can explode. Flammable solids sublime hence their vapors are just as hazardous as the vapors from a flammable liquid. For example, glacial acetic acid (solid or liquid depending upon the temperature) is a flammable chemical as defined here. Keep in mind also that the vapors of most flammable are denser than air and can travel several tens of feet, or more mixing with air of course, but without dilution to less than 1%.
Precautionary measures include the enforced absence of ignition sources, such as lighted burners, heated surfaces (the class envelope of an ordinary lighted incandescent light bulb is hot enough to ignite some vapors), sources of sparks -- electrical including static charges and ignition sparks. Keep containers closed when not actually in use. Insure that the air movement in the laboratory is sufficient to keep the concentration of the flammable vapor in the air well below 1%. Minimize the quantities available -- usually 100mL is more than ample. Store in safety cans in an approved flammable liquid storage cabinet. Glass vessels (test tubes, flasks, etc.) that will contain flammable gases or vapors and handled by students or used by teachers in demonstrations should be taped beforehand to minimize flying glass shards, and used only behind a sturdy shield that will confine any flying parts.
Ask your local fire department to review the procurement, receiving, storing, handling, dispensing, use, and disposal of flammables and to make recommendations for improving safety.
Clearly, when using flammables, eye and face protection is mandatory, and, depending upon conditions, thick gloves and body and limb protective pads are also indicated. Make certain in advance that the safety shower is working and that students know how to use it. Insure beforehand that fully charged Class B fire extinguishers are available, that you and the students know how to operate, that there has been held a recent, successful, fire drill, and that the fire alarm system is operating and all persons know what the fire alarm bell sounds like. Depending upon the local conditions, you may wish to instruct students in the use of afire blanket, to "drop and roll" if their clothes catch fire, or to walk calmly to the safety shower, or some combination of these.
A corrosive chemical either destroys living tissue or causes permanent change in such tissue through chemical action. (A chemical that corrodes iron, for example, wet sodium chloride, is not corrosive under this definition -- which pertains to chemical safety. Ten molar sulfuric acid will corrode iron and is also a corrosive in a safety context.) Corrosives destroy skin and tissues under the skin. They destroy eyes, respiratory tract tissues, etc. The corrosive effects can be impaired sight or permanent blindness, sever disfigurement, permanent sever breathing difficulties, even death.
Usual precautionary measure include preventing contact with skin,m eyes, and respiratory tract. Wear eye protection and a face shield. The eye protection should fit around the eyes so as to prevent splashing around an edge and into the eye. The face shield should be a so-called full face shield, large enough, and curved, so as to protect the whole face, neck and ears.
Wear gloves made of a material known to be impervious to the corrosive being handled. Be sure the gloves are free of corrosive contaminant on the inside before wearing. If it is likely that bare arms will be splashed, wear sleeve gauntlets made for the same material as the gloves. Use a lab apron, made of a material known to be impervious and large enough and full-tailored to protect the clothing. An apron tied so as to not protect the lower neck/upper chest, or not long enough to protect the calf of the leg is inadequate.
III. Work Habits