Double-check my rationale and math(s)

[Altair_the_Vexed]

I've got a small canister of a 350 ppm carbon monoxide / air mix. It holds about 110 - 120 L of this mix.
My lab is 2.5 m tall, 8.0 m long, and 4.0 m wide. I make that 80 m^3, which is 80 000 L.

If I allowed all the gas in the canister to escape into the air, and it mixed evenly, I calculate that I'd have 0.5 ppm of carbon monoxide in the lab's air.

Have I got this right? Did I miss anything?

(Context: I work in an electronics lab, and I have a CO gas detector to test, which requires that we use this CO mix. No-one else in the lab has even the slightest clue about chemistry or health and safety. It is not a regular thing for us to test, and we will most likely never have to do it again. The legal occupational exposure limit in my country is 20 ppm for long term exposure, and 100 ppm for short term (about an hour or so).
Also, I won't be relying solely on the posts of the Playground, in case you're worried. I've got a Health and Safety department to fall back on - I just don't want to present figures to them if there's a stupid mistake in them.)

[DeTess]

Assuming the there is no CO in the air beforehand that sounds about right, yeah. Do note that it might take a while before it is perfectly mixed in with the rest of the air though.

[DavidSh]

Is the canister at ambient air pressure and temperature? If not, is that the volume of the canister, or the volume that the contents would occupy if allowed to expand to ambient air pressure and temperature?

Otherwise everything sounds about right.

[Altair_the_Vexed]

Is the canister at ambient air pressure and temperature? If not, is that the volume of the canister, or the volume that the contents would occupy if allowed to expand to ambient air pressure and temperature?

Otherwise everything sounds about right.

The volume I gave for the canister is its nominal depressurised volume - i.e. it's about 1.5 L pressurised, but it'll be about 120 L at room temp and pressure.
My lab's at 200 m above sea level, so fairly standard.

I like that the Playground asks the right kind of questions. It gives me confidence I'm on the right track too.

[veti]

Assuming the there is no CO in the air beforehand that sounds about right, yeah. Do note that it might take a while before it is perfectly mixed in with the rest of the air though.

And assuming the lab is airtight, which is an unusual property for electronics labs in my experience but I don't know yours.

[Brother Oni]

Have I got this right? Did I miss anything?

Your H&S officer looking very worried and checking the fine print of the site insurance.

As per the HSE guidance (https://www.hsl.gov.uk/media/1188337/carbon%20monoxide%20(co)%20in%20breath.pdf), the Short Term Exposure Limit for CO is NMT 220 ppm in a 15 minute period.

Since you can't guarantee even mixing, you're going to have to either open the container and run outside, or have breathing apparatus if you have to stay in the room while it dilutes down to safe levels. You may or may not have to do some supplementary calculations to estimate the time until the CO has mixed enough to drop below the STEL and the TWA (30 ppm) before you're let back in the room.


And assuming the lab is airtight, which is an unusual property for electronics labs in my experience but I don't know yours.

For the purposes of this experiment, assuming that the room doesn't have an AHU or a HVAC connection, closing all the windows and doors will be sufficient to treat it as an enclosed box.

It's certainly sufficient to cause inert gas asphyxiation - one place I worked used tonnes of liquid liquid nitrogen a week for freeze-drying and it was drilled into us that if you see the low oxygen alarm go off, RUN.

[Altair_the_Vexed]

CO is toxic, of course, not an asphyxiant.
I'm trying to work out my worst case exposure here - the actual amounts I'll use will be in the order of my, not 10s of L.
I'll have plenty of ventilation and deliberate air mixing to avoid any build up in a location.

[Fat Rooster]

Your maths checks out, but I think you want to enclose the detector and test it isolated rather than trying to make the whole lab toxic. Unless it is a specialist CO detector for specific chemistry reasons it is doubtful it is going to go off for 50ppm before the gas disperses, never mind 0.5. You would probably get higher levels than that from a few candles placed around the lab.

The mix you have is seems like it is already designed for testing detectors, and is not designed to be diluted.