Listening to commercials, one would think that chemicals are harmful and should be avoided.

Ads for carpet cleaning, household products, toiletries, pet foods and other products claim to be chemical-free. The implication is that we should avoid chemicals in order to promote health and safety in the home and in the environment at large.

Exactly what are these nefarious substances known generically as chemicals that we should avoid?

One carpet-cleaning firm claims to use only water but no chemicals. An acne medication claims not to use chemicals but contains a list of substances that most of us cannot pronounce.

What is a chemical, anyway? There seems to be some ambiguity even among the arbiters of word use.

One dictionary defines it thus: “Produced by or used in a reaction involving changes in atoms or molecules.” Another says, “A substance with a distinct molecular composition that is produced by or used in a chemical process.” Yet another: “A substance obtained by a chemical process or producing a chemical effect.”

None of these tell us what a chemical is in a way that allows us to know whether a given substance is a chemical.

There is an unambiguous way to decide: All matter consists of various elements and chemical compounds that are often intimately mixed together.

To put it bluntly, everything is a chemical. Claiming a product to be chemical-free is actually saying it consists of nothing. Emptiness. A vacuum.

For example, water is one of the most corrosive chemicals. It is the universal solvent, capable of dissolving more other substances than any other chemical.

So what are these claims really trying to say? Do they mean no “harsh” chemicals, no “damaging” chemicals, no “unhealthy” chemicals, or are they just relying on the ignorance of consumers to make it sound like there is something that isn’t?

There is the problem of defining what kind of chemical their product does not have. Water can leave a permanent stain on a wood surface, while another product that does not contain water may be useful in polishing and preserving the wood but be poisonous. That same product might produce permanent stains and ruin a silk dress.

The word “chemical” needs context that relates it to a particular product and use, in the same way that “speed” is absurd when deemed a cause for traffic accidents when the correct description is “excessive speed” or “speeding.”

For example, “no harsh chemicals” are used in this product, or “no corrosive chemicals,” “no harmful chemicals,” “only safe chemicals” …

Perhaps it is only a handful of chemists and other scientists who are offended by this miscarriage of locution, but it is nonetheless incorrect and makes the companies suspect of either ignorance or deception.

When you hear that a product is chemical-free, first of all be suspicious of the intentions, then find out what is really in the product and make an informed decision about whether the chemical ingredients are caustic, harmful, hazardous, harsh or harmless.

The one thing you know for sure is that no product is chemical-free. Even the air we breathe is a chemical.

Richard Brill is a retired professor of science at Honolulu Community College. His column runs on the first and third Fridays of the month. Email questions and comments to brill@hawaii.edu.