I'm jealous

, it is very very strictly regulated in most countries, usually only sold to company owners or such. If it is really over 90% pure and the cylinder does not leak, it is quite a reliable way.
May I ask where you tested your cylinder for 30 seconds? In a large room or outside / balcony? Because 30 seconds are a lot of time to be breathing CO in a small room to not feel anything. Did you feel headache or nausea after your test?