Here a comment I found at another site about H2O2 with stabilizer found in pharmacy:
“The H2O2 must NOT be the drug store H2O2, but a chemical supply H2O2 type since they typically add a cancer causing stabilizers, mostly to discourage H2O2 use.”
The recommendation was about using H2O2 internally I.e. drinking it with water.
For inhalation I would trust Bill Munro who used regular 3% H2O2.