Can I Give My Cat household 3% ONLY?

No
Hydrogen peroxide causes severe hemorrhagic gastritis in cats. There is no safe at-home emesis for cats.
Source: Merck Veterinary Manual
Already ingested? Pet Poison Helpline 855-764-7661

Skip it or ask a vet first if

cats, nevercaustic/petroleum ingestionalready vomitingunconscious or seizingbrachycephalic breeds without vet direction

The safe habit

Confirm any medication decision with your veterinarian, who knows your cat's health history and other medications. VetDose shows published reference data, not prescriptions.