I think it’s important to understand that if the whole Internet just shut off in an instant, life as we know it would cease to exist. I’m not talking about a cultural change. I mean millions of people starving and freezing to death because literally everything you take for granted today is ordered, scheduled, and delivered using the Internet. That means no food deliveries, no fuel deliveries, no imports or exports, no trains, trucks, or planes moving, no payments or money transfers. Nothing. Oh, and all the emergency services that you’re going to need will be unable to respond because no phones and no communication from dispatch centers. We don’t know how to do business without the Internet anymore, so if it goes away, there goes your way of life. Building that back to the “old way” will take way longer than you or your neighbors are likely survive competing for essentially nonexistent resources.

But for those who manage to survive, I would say party like it’s 1899!

You are indeed, but it points to a fallacy in the original question. It’s not universal basic income if it is stipulated that you have to do something to receive it.

I used to calibrate industrial gas detectors. They generally have an active air sampling path with a pump and a sensor in the gas flow path, and we would calibrate them by flooding the sensor chamber with a test gas at a known concentration. For the type of sensor you have none of those conditions exist (no controlled gas flow path and no pump) so there is essentially no way you can accurately test their response. You essentially have to trust the manufacturer to have made a good product. The one thing you can do is look for an install date and (hopefully) an expiration date, if you can inspect the back of the detector without setting off any central alarm system. If you really don’t trust the owner’s sensors, you can always buy and use your own. Just make sure you place them carefully according to the manufacturer’s instructions.

Also, your detectors are probably combo smoke/CO, but not natural gas. You would smell the odorant in the gas long before the concentration becomes dangerous so a detector would be redundant.