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Comment by Animats | Hacker News Reader

Here's a "vape detector" with more explaination.[1]

It contains an air particulates detector and a CO2 detector, plus humidity, temperature, and noise and light sensors. They're probably looking for particulates and CO2 ramp up, hence the "algorithm". It's not clear how accurate this is, but it's not mysterious.

There's a version sold to schools that adds "bullying detector" capability. This adds detection of "keyword calls for help, loud sounds, and gunshots."

[1] https://fobsin.com/products/mountable-air-quality-vape-detec...

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It sounds ludicrous to say out loud, but if you're staying in a Hyatt hotel, it's best not to take a hot shower until this issue is resolved. The steam from the showers tend to make these types of particle sensors go wild.

Even outdoors, humidity is a problem. Humidity turns little particles into bigger, soggier particles that give higher readings on optical sensors, which can rather inflate readings on cheap sensors in humid or foggy conditions. There’s a reason that the actual EPA particle counting standards involve drying the particles before measurement.

(RIP, EPA.)

The smoke detector in my previous condo used to go off all the time when I showered. Had to remove it shortly after moving in lol

Must have been placed improperly. They should not be installed in kitchens or in or near bathrooms.

But also, you should run the exhaust fan in the bathroom when you shower, this removes at least some of the moist air and cuts down on the chance for moisture damage and mold to develop.

It was in the hall right outside the shower, the exhaust fan didn't work very well so I left the door open. I live in a different place now and no longer have that issue.

But the point is that machines are not particularly good at detecting smoke lol

Smoke detectors detect microparticles in the air. They typically don't or can't differentiate between steam and smoke, at least not the cheap household type detectors.

> They should not be installed in kitchens or in or near bathrooms.

But then you can't catch vapers in the most popular vaping place: the bathroom. Oh no! Our revenue stream! It's broken!

I think, elephant in the room here, smoking is conspicuous and does real, tangible damage. Vaping? I'm not so sure.

Yeah vaping is lame but does it actually harm properties? I mean, if someone vapes 10 feet from me I can't smell it. And if I can smell it, it's gone in < 5 seconds. There's no smoke in it, it doesn't linger.

The issue is not a Hyatt issue. It is an issue with a specific hotel that happens to be a Hyatt.

That makes it a Hyatt issue

Why would CO2 be caused by vaping? And surely the amount of CO2 caused by a cigarette is dwarfed by the amount exhaled by a person?

A person outputs about 1kg of CO2 per day, which is less than 1 gram per minute. A cigarette weighs roughly a gram, which means it probably emits roughly 3 grams of CO2... or less... (The O2 comes from the environment, and weighs 32 to carbons 12, but the cigarette isn't actually pure carbon).

I don't know... that's maybe detectable? You'd need a pretty sensitive CO2 sensor and to be tying it to other signs to avoid "someone else walked into and out of the room"... but in principle...

> A person outputs about 1kg of CO2 per day, which is less than 1 gram per minute.

I'm skeptical about this. Normal adult tidal volume is about 500mg, with a normal respiratory rate of 12/min, so 6L/min. Normal air is about 0.05% CO2, so you're at 3 grams/minute atmospherically that is inspired and expired.

We actually output closer to 4% CO2. 240ml/minute. With the windows and doors closed in my 10x20 living space and 4 people, CO2 can easily go from a baseline 4-500PPM to over 1000 in an hour. That's not 240 grams of CO2 doing that.

https://airly.org/en/the-composition-of-inhaled-and-exhaled-...

For what it's worth here's a NASA document using the same 1kg/day number: https://ntrs.nasa.gov/api/citations/20090029352/downloads/20...

I don't know where I originally got that value from, it's one that has stuck in my head for years.

You're mixing your units -- 0.05% of 6L is 3mL. In order for that to weigh 3g, atmospheric CO2 would have to be as dense as water.

Most figures I see peg 1mL of CO2 at closer to 2mg (it's about 50% heavier than the equivalent atmospheric volume, since that's mostly N2 with some O2). Your estimate of 240 mL / minute is about 346L per day, or about 700g of CO2. That's roughly the same order of magnitude as the cited 1 kg / person / day.

edit: Another way of thinking about it: if you scale up your numbers to grams per day, you'd end up with a ludicrous 346 kg / human / day. Multiply that by 12/44 (mass of Carbon-12 vs CO2), and that's the equivalent of a human shedding 100kg of carbon every day from just breathing. Most humans don't even weigh that much.

You're absolutely right, I apologize - I did mix units, and my thoughts collapse from there.

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