The likelihood of encountering carbon monoxide in a Port-a-potty is almost nonexistent. There is no combustion going on inside the toilet vault. You might encounter some carbon monoxide if someone set the Port-a-Potty on fire but there are other concerns in that event.

Yes, there are some sulfur compounds present...hydrogen sulfide being the most prevelent and the most dangerous...but those are in very low concentrations. Animals can detect sulfur compounds at extremely low concentrations...0.47 parts per billion is the human detection threshold. Toxicity occurs at about 350 parts per million or about 350,000 ppb. A ppb, by the way, is a pinch of salt in 10 tons of potato chips or one second in about 32 years (32 years is about a billion seconds). I've been in some rank PortaJohns but nothing that rank.

Porta-a-Pottys are also ventilated so that cuts down on the gas build up. You don't want to have people using them falling over dead...it's bad for business.

As for reaching down into the vault, I'm not going to test this but I reasonably certain that an average adult could reach each corner of the vault from the toilet seat with just a bit of stretch. A dropped item like a phone isn't going to migrate to the outer corners quickly either. There's a lot of,um,stuff...the one place where it would be appropriate to use the proper word and the filters won't allow it...in the way.

I suggest using a lanyard on the sunglasses if the porta-potty fumbles is a particular issue.

All I am saying is there is ventilation above the toilet seats, but not necessarily below them. I work in a broad environments where there are more than just port-a-potties (CO, Methane, Sulferous gases, etc), and they all are heavier than oxygen and can lower the amount of oxygen. The key thing is that if the oxygen concentration drops below the right level, it can cause problems.

It's just worth being cautious and not stick your head in below the toilet seat. I tend to ride in places where the toilets are vaulted toilets not port-a-potties, and I would not be able to reach things. I only encounter port-a-potties in races, so yes I probably could reach a phone in that environment, but most toilets I encounter I couldn't.

Anyway, enough of that. I only wanted to note that there is a legitimate risk of death, and as long as someone is aware of it, they will improve their chance of survival and could perhaps retrieve a lost item. It's better to be cautious than to assume it isn't going to kill you at all. Look up information about confined space deaths. They happen, mostly because people think it can't happen to them. It can, and it does.

Time to provide an update:
My Halo II headbands arrived on Wednesday.
Sweat Gutr and Cavalo sunglasses have been ordered.
But looking at the weather forecast, rain is predicted all 5 days of next week, which means I wont be able to try them out anytime soon
Don't you just hate it when this happens? You get new stuff but you have to wait before you can try it out?

yep I got a new bike last year and had to wait over a week to ride it due the rain...

but now that I have it is sweet! enjoy the ride when it comes

The disgusting discussion was about idiots dying while retrieving their phones from Port-a-Potties, not vault toilets. A Port-a-Potty has a vent pipe that runs from the vault to the ceiling of the unit so that you don't have build up of gases. Even vault toilets have vents so that the unit doesn't build up gases. Even vault toilets are vented well enough that people can survive in them...and I just gotta say Eww!

Yes, I know the dangers of confined spaces but Port-a-Potties don't fit into that category. If they did, the whole Port-a-Potty would be a dangerous confined space.

They work in the rain too.

Hahahaa. Good point. I have only recently started commuting, so I am sticking to dry weather commutes for now.

keep a small cloth in your pocket and wipe.

I think it is time to provide an update.

I got two Halo II sweatbands as well as Gutr band, along with riding glasses.
I have been switching between the bands now for a few days, and at times both Halo II and Gutr have eventually failed in stopping the sweat from getting into the eyes. I guess it is just a combination of 90 degrees weather plus me sweating like a pig. Between Halo and Gutr, I do prefer the Gutr though, mainly because it is easy to reuse it, whereas Halo II bands need frequent washes and also need to be a pair.

I read in one of the randonneuring blogs that "two is one, one is none". I think it applies to commuting too.

I'd be slapping a bandana under my helmet to try and stop some of the sweat.

Then I will have to carry two bandanas and two sweat bands and give up on feeling the wind going through my helmet

I swear by the Halo skullcap. I wear it EVERY time I have my helmet on. Not only does it keep sweat out of my eyes, it also keeps my helmet pads from getting nasty. I've had my current helmet 2 years and have never had to wash the pads because the skullcap keeps junk off of them.

For glasses I use Tifosi half-frame glasses with a 1-piece photochromic lens. The half frame means no blind spots when looking back over my shoulder. Photochromic lens is suitable for both day or night time use, and the 1-piece lens provides great coverage for keeping dust and other junk out of my eyes, which was a BIG problem before I got these glasses.

I tried the Sweat Gutr band some years ago, didn't work for me at all I think because I was leaned forward on my road bike. The Halo skullcap works much better.

Now that you mention it, every time I've had sweat overflowing from either the Halo band or the Gutr band, I've been in a forward leaning position, head tilted down.

Will have to give the skull caps a try now.

Thanks for the recommendation!