mold remediation / water damage

[Guest guest]

We just found that there was a big water damage bathroom and drywalls.

I had one of the big companies come in and they started immediately.

Dehumidifier ... No panic, I am not in the house at the moment.

In the contract they say they want to use chemicals if necessary.

Does anybody know which chemicals would be eventually ok, if necessary?

Which chemicals have to be avoided?

Are chemicals necessary if the drywalls anyhow have to be replaced.

Thanks for any input.