Formaldehyde is a kind of chemic gas.

On occasion I have seen rental properties with signs posted on them like this:'Warning, this site is known to have chemicals known to cause cancer'The sign may or may not list specifics, such as asbestos, lead, ect.Are owners forced to put up these signs by the city or county?

It didn't hold up well and it was highly toxic due to all the formaldehyde and other chemicals used in the curing process.

Often you have the ability to check for previous fires, chemical issues and ambulance transports.

My sister went there once, she said there were mosquitos or horseflies as big as small cars, and some truck drove down the beach a few times a day spraying clouds of chemicals to kill them.I can't get that picture out of my head.

According to him the chemicals can get leached into the studs, can't be treated, and even after the house has had all the drywall replaced they can affect the air quality. 

We have a lot of oil field service companies, chemical additives for oil wells, drilling pipe, motor rewinding, dirt contractors, construction/moving equipment, rental equipment, workover rigs, consultants, etc.

Trucking, construction of drilling pads, pipe, testing, drilling mud, chemicals, casing, etc. 

I wouldn't risk having major chemicals in a place I had to reside or rent out.

That is a chemical that makes you feel good and relaxed.