At least one individual has responded to a remark I made in an earlier post which mentioned, in general terms, the derailment of chlorine tankcars.

Chlorine is best thought of as a powerful irritant rather than a toxin, because persons who die from chlorine exposure die from the irritant effects. Chlorine will attack the mucous membranes of the body causing weeping, running nose and mouth, and edema of the lungs, a sort of quick pneumonia that drowns the victim in his own body fluids. (Chlorine is the basis for several war-gases, such as mustard.)

Chlorine is transported in railcars under pressure, so that the chlorine inside the tank is actually liquid. Even though the cars are equipped with shields to prevent puncture during derailment, releases do occur, as they do with some regularity in industrial applications such as water treament. Damage to tankcars during derailment may be incurred as a result of sideswipes with other cars or stationary rail features, which produce long scores or gouges in the steel. If a train is moving very slowly, as is often the case in populated areas, the chance of a derailment leading to a release is very small.

But if a train is moving quickly and a derailment damages a tankcar, the results can be catastrophic. A large puncture may spurt pure liquid chlorine (not to be confused with the chlorine solutions sold to treat swimming pools, etc.). That liquid will almost instantly become a gas, and travel with the wind, along the ground, chlorine being somewhat heavier than air. In rare cases the entire contents of the vessel may be discharged at once.

If you smell chlorine in the air (not just bleach, or a nasty swimming pool) you should breathe as little as possible as you move quickly at right angles to the wind. If you can see a cloud approaching (chlorine is a sort of yellow-green) get away from the cloud in the same way. A few deep breaths of even moderate concentrations of this material can kill you within a few hours.

Never attempt to drive through a chlorine cloud. Chlorine in sufficient concentration will stall your car at the worst possible moment. If you must run through a cloud for any reason, take a deep breath of good air (if available) and pretend you are underwater; you will probably be allright. When you get to safety, remove your clothes, as they tend to trap the gas, and walk around to air yourself out.

Chlorine leaks are typically mitigated by off-loading to a more viable container. The process can take hours or days depending upon the circumstances surrounding the accident, and may be fraught with hazards of its own. I would strongly suggest leaving the area of a derailment even if you are in a "safezone".

If you receive an order from emergency responders to "shelter-in-place", you should probably obey it. Shelter-in-place means remaining in your home or workplace as well "sealed-in" as possible. Heating, ventilation and AC should be off, doors and windows closed, and preferably taped. The idea is to allow a cloud to blow by, while you breathe the air inside your structure. The proceedure can save your life. If, however, you are accustomed to receiving such orders several times a year, you should probably move out of the neighborhood asap, as this suggests that no one is minding the store.

These suggestions are generally applicable to most chemical release scenarios, but I am thinking in terms of water-reactive irritants (including ammonia). Hope this helps...

-- james hyde (hydesci@gte.net), January 04, 2000

Answers

I'm the one who requested this info, as we live so close to railroad tracks. Thank you for taking time to provide this - I'm printing it now.

BTW, does anyone have a good link for shelter-in-place information?

Thank you,

-- Appreciative Lurker (Lurking@homewithfamily.com), January 04, 2000.

Start with FEMA. I'm guessing they will have more links than you'll ever want or need for state and local agencies. Shelter-in-place and other procedures are the province of local firefighter and hazmat brigades. Info should not be hard to find. Search your Local Emergency Planning Council online as well.

-- james hyde (hydesci@gte.net), January 04, 2000.

This link was provided by Ashton and Leska some weeks ago and has very good information. Sorry I am hot link impaired: http://franklinem.org/shelterin.html

-- Nadine Zint (nadine@hillsboro.net), January 04, 2000.

NO....if Chlorine spills near you - NEVER shelter in place against that gas.

This is immediately and permanently deadly in large quantities....no house is airtight enough to prevent Cl from leaking in, and the amount (from a large spill) of gas outside is sufficient to harm people inside a house even if most of the poison is kept outside the house.

I've advised "shelter in place" in the event of fallout - because the house walls prevent your exposure to the contaimination outside.

Poisonous gasses are different - IF a spill occurs, get upwind immediately. Now, whether one will happen is unknown - so far, there have been no obvious train wrecks from bad schedules or switch control failures. ..... But they can occur - a wrecked tanker truck on a highway (in Houston I believe) many years ago killed several, hurt many others in a simple collision - so failure (toxic spills) is possible from other reasons.

-- Robert A Cook, PE (Marietta, GA) (cook.r@csaatl.com), January 04, 2000.

Dear PE,

One cannot speak in absolute terms regarding hypothetical scenarios, but shelter-in-place can be a very good call for chlorine. By the way, the plural of gas is gases.

-- james hyde (hydesci@gte.net), January 04, 2000.