In the end, we can't legislate common sense, nor can we abdicate responsibility to those above.
(The opinions above are mine and of anyone who agrees with them.)
Kenneth JT Livi
Kenneth:
Your students are correct, it's the safety officers who are in
error. Any good safety manual for cryogenic gases specifically recommends
sandals, and *against* shoes, gloves, and the like.
The reason is the Leidenfrost effect. The LN2 droplets flash-evaporate when they hit bare skin, producing an insulating layer of gas, and prevents freezing damage. Assuming it's a quick spill, and not continous contact. Shoes, glove (including asbestos gloves), and any other clothing that confines the LN2, and cold gas *will* cause freezing.
A face shield is a good measure, byt the gloves and any other similar regs are dangerous.
Philip Oshel
oshel@ux1.cso.uiuc.edu
Try getting your safety officer to conduct an experiment:
1. Hold out hand,
2. Pour a small volume of liquid N2 over hand
3. Now the interesting bit - put on a glove, and pour the same quantity of
liquid N2 into glove.
4. Phone for ambulance.
The point is that a brief contact causes no problems, but if the contact is continued you get a nasty burn.
Gloves, goggles, masks (and shoes) are actualy more dangerous when handling liquid N2 than sandles and no protection. And clothes are actually more dangerous than being naked. Get the safety officer to experiment. With a little persuasion you can probably convince the safety officer that when handling liquid N2, everbody should be naked.
More seriously, bureaucrats, administrators and the inexperienced should talk to somebody who has real knowledge.
Dr. Larry Stoter
Larry@teknesis.demon.co.uk
As a wild and fun loving farm boy who went into science, I found LN2 to be a wonderful toy. The closest I ever came to danger was when an associate put some in a nalgene bottle and closed the top, resulting in a frozen plastic flask going "POP".
We did stunts along the lines of freezing the contents of our associates lunch pails, shattering a fish (boy was that an ultimately smelly mistake !), and once when we froze a rubber tube in the neck of a dewar by mistake, we had to empty the entire 50 liters into a trash container.
Consider the heat of evaporation, compare it to the heat of condensation of steam, and think how many burns YOU personally know of from that source vs. from LN2.
I am repelled at the lack of savy and the excess of fear instilled by the law ("profession") regarding such pseudo threats as LN2.
The presumptive (and ignorant) reaction is irrational, but accfording to the same principles, TWO safety officers should come in the box containing each microwave oven, a gun should bear a judge attached, and an auto, a member of the supreme court, or a receipt for $1000 from your favorite lobbyist. Remember, not only can the law be bought, It's really CHEAP ! !!!!!!
Ed Monberg
em@mediacity.com
Dear Ken,
You're right about not being able to legislate common sense. In the case of
liquid nitrogen, I have seen LN2 slopping out of styrofoam cups onto peoples'
clothes, into instruments, all over papers, etc.
For all of the examples everyone can cite of *unnecessary* regulations, I am still amazed to see kitchen microwave ovens in labs being used to heat toxic chemicals, including fixatives and heavy metals, the fumes from which then "ventilate" into the open lab when the door is opened. In some cases, the oven is then used to heat coffee and/or lunch.
Steven Slap
75767,640@compuserve.com
> Gloves, goggles, masks (and shoes) are actualy more dangerous when handling > liquid N2 than sandles and no protection.True with the exception that the shutoff valve handle on a big LN2 tank will get cold enough to be dangerous, and does not exhibit the leidenfrost effect. Using a glove or other insulation when turning off the LN2 after filling the dewar makes good sense.
> > More seriously, bureaucrats, administrators and the inexperienced should > talk to somebody who has real knowledge.A great general rule. Reading the manual also helps, and every lab should have a safety manual on hand.
Bill Tivol
tivol@wadsworth.org
Greetings,
I've read with interest the comments of others questioning liquid
nitrogen safety regulations. In spite of many years of pratical experience
with the stuff and being a trained safety officer, I took some time to
examine the subject. I disagree with those who have problems with the
regulations. The regs seem to be aimed at preventing continuous contact
and the resultant injuries.
In the CRC Handbook of Laboratory Safety, 3rd edition, pages 315-317, lists all the basic precautions (face shield, impervious clothing, etc.). For those who disagree, gloves are optional.....except, as Tivol pointed out, when in contact with cold metal parts. The CRC actually suggests using some sort of potholder to protect hands from the metal. The CRC also points out that efforts should be made to prevent trapping the cryogen. When trapped against the skin, LN2 will cause injury since the contact is no longer momentary and becomes continuous contact. Cuffless pants worn over the shoes/boots are reccommended, i.e.spilled LN2 that gets trapped inside a shoe with the foot may cause injury. For those who suggest sandals as appropriate should think about the possibility that with a major spill, some LN2 could be trapped beneath the foot or under the strap of a sandal, possibly causing injury. Appropriate shoes can protect the foot for short periods. If the footwear is frozen, generally it can be removed before injury occurs. If gloves are used, the fit should be loose so that they may be shed quickly...ala a hockey player's actions when he has been treated less than courteously by an opposing player. The problem I have with faculty and staff is the use of latex gloves while using LN2. The Leidenfrost effect can definitely cause injury if the latex freezes against the skin. For those who would not wear appropriate gloves, have you considered the possibility of LN2 being trapped under a watch band, or under a ring? In a major splash, could LN2 become trapped at the beltline, between the pants and shirt? The whole idea is to make sure that most any cryogen does not get trapped against the skin. If you can handle LN2 safely without protection, or have done it for years without incident, more power to you. I hope your luck holds out.
Interestingly enough, Air Liquide, a national supplier of cryogens, also lists similar precautions in the use of liquid nitrogen and other cryogens.
Texas Tech has (arguably) a large number of beautiful women, but they are not the ones coming to get liquid nitrogen....and of the individuals who do get LN2 from our lab, I would rather them come clothed.
Charles J. Butterick
email emccjb@ttuhsc.edu or
chuck@micron1.lubb.ttuhsc.edu
Just another late word on the LN2 issue. There are crogenic gloves available which will properly protect your hands when handling liquid nitrogen or shutting off frozen valves and handling frozen hoses. Although I agree that sometimes safety issues don't necessary reflect common sense, having the gloves doesn't hurt.
Melanie Behrens
behrema @ Texaco.com