David Viola, age 11, of Pairfield, Connecticut, for his question:

What happens if you puncture an aerosol can?

Nowadays all sorts of different things come in handy aerosol cans. If you happen to puncture the wrong one, you may not be around to enjoy the results of your experiment. The contents in an aerosol can are squeezed in and sealed under pressure. Gases and liquid droplets can be compressed in this fashion    but they seem to detest their crowded imprisonment. When somebody makes even a tiny puncture in the can, they escape outside to free¬dom with force and fury. Some aerosol contents happen to be dangerous chemicals which could cause great harm if you were accidentally exposed to them.

Chances are, you have handled an aerosol can of paint. Now ordinary paint is fairly harmless, but paint from a punctured aerosol can zooms out at super speeds in all directions. It seems to have an urge to aim at your face and hit you in the eye. A direct hit can be dangerous, very dangerous to the eyesight and the problem should be given expert medical attention in a hurry. The contents of any punctured aerosol can tend to aim at your eyes. Even when the chemicals are known to be harmless, this needs prompt attention. And the escaped contents, harmless or otherwise, always spread themselves over an area of several feet in all directions. This calls for a tiresome clean up job and what's more, the contents of the can are lost.

Sometimes the little jigger at the top of an aerosol can refuses to do its job. This is annoying and tends to make a person impatient. The tempta¬tion to puncture the can to get the stuff out is very strong. But it does not work. The contents are sealed under pressure and out they splatter in all directions. The labels on most of those cans says that they should not be exposed to a lot of heat. Heat causes them to burst and the shattering

result is worse than a mere puncture. If tossed into a hot furnace, even an empty aerosol can may explode. All of these ghastly possibilities are hinted on the cans. The simplest way to control the situation is to read the instructions    especially the warnings that tell what not to do    and heed them.

In many cases, there is a subtle bit of information that may escape your attention unless you are very alert. Some aerosol sprays spread forth fumes which may stifle your breathing apparatus. The labels give instruc¬tions on how far you should stand from the spraying operation. Some suggest that windows and doors should be wide open to allow airy ventilation during, and for some time after, the operation. Just by following the instructions on each can, you can avoid a lot of unpleasant surprises, some messy and some downright disastrous.