Where do you guys draw the line where you aren't willing to explore a place if it is contaminated? I know a lot of places that are filled with asbestos, but as long as I am wearing disposable clothes and a good P-100 cartridge mask then I feel fine going there. At what point is a place so contaminated that you wouldn't be willing to explore it? Are there any exceptions you've made for a specific location? Speak in general terms, no location reveals.
-Bygone Era

I haven't encountered a location too contaminated for me yet, including an abandoned testing range so full of UXO that it'll never be safe to redevelop (it sounds a lot more dangerous than it is, just avoid digging in certain areas or kicking metallic objects on the ground). Granted, an active minefield, extreme chemical danger, or potential radiation hazard would all give me pause, but asbestos and black mold aren't something I worry about since I use a P100 respirator when necessary.

Not had to draw the line yet, except for structural stability reasons.

For me, most superfund sites(at least in the US and territories) are way too toxic for me to consider, but there has been an old paper mill that has been on my radar for a while. I think a place like that, while it would take a lot of time, prep and safety equipment, in the end, I think depending on how well maintained everything is there(like if everything they used to use is still there) it would be worth it, but otherwise, my line I draw is normally at whether the EPA has it on the NPL. Also, anything with UXO is something I don't mess with.
-Bygone Era

I haven’t drawn that line yet. Structural or legal concerns (police presence) have been the more frequent line for me

Also gonna go with structural & security related concerns. Asbestos, black mold, and copious amounts of rat poop haven't stopped me yet. Radiation was a good deterrent up until recently. Anyone else carry a geiger counter?

I agree with structural issues.

I will admit, there have been one or two places that the stench was too much for me and I had to bail. The worst was a granary full of some kind of wet, rotten wheat. I’m pretty sure that shit was toxic. Definitely flammable.

I have a lot more concerns than asbestos usually, but since this thread seems to be specifically about that, okay.

My sister used to have a job overseeing restoration of a government building that had been abandoned for years, and she got me inside at some stage. We had to wear respirators due to asbestos, but there were some levels she said we couldn't visit, because they were doing active asbestos abatement. According to her, the usual respirator is not able to protect you in that environment. The guys working on that floor had bodysuits and a more extreme kind of mask, which I never saw.

So I would stay out of places if they are removing asbestos.

It's probably not the kind of exploring you have in mind, but I had to think about this a lot back when I lived in Atlanta, with the drains. The Atlanta drains are combined sewers, so there are no clean storm drains to explore like many cities. In that case, it became a question of personal comfort. I went into drains I could easily stand in, during dry weather, to minimize risk of muck. Anything smaller would make it hard to minimize contact with walls and the ceiling, and I wasn't too eager to touch any of the gooey buildup on the surfaces, even with gloves. I wore a dust mask to filter out the nasty particles and gloves so I wouldn't put my hands in anything gross. The one trip I made into those drains was short-lived, and I don't think I'd be ready to go in deeper without waders, at a minimum. Even then, it might be a little gross for me. It's a shame, though, because what I did see of the drains there was damn impressive and I'm sure there are some amazing spots in the city.
I guess it really comes down to the amount of PPE you have, how equipped you are to handle any accidental contact with contaminants, and the level of risk you're willing to take.

Honestly I care less about asbestos than I probably should, but even with stuff like that, black mould, etc, I'll usually go in and out real quick just to look around.

I once happened upon an abandoned building with soooo much rat shit, the stench hit me like a wall as I stepped into the room. I still went in, but I didn't love the experience.

There's an abandoned building in the town adjacent to where I live that is the only place that I would draw the line at for non structural reasons. It was some sort of old industrial building with a large garage that the town bought for a DPW storage facility. It had large factory windows on the top floor, which somebody apparently left open. Pigeons began to roost on the upper floor of the building, but it must not have seemed like a pressing issue, because nobody did anything about them. Eventually, the pigeons generated to much poop that the building was contaminated to the point of being completely unusable. It seems like a really interesting building, but that is a line I will never cross.

Not gonna climb radio towers.

Sewers are just drains that smell worse and kill you more easily, so no point there imo,

I don't break anything. Better to find a creative way around.

Spots with asbestos are off only bc I've lost my respirator and I usually don't find the spots particularly interesting regardless.

I will give up on a climb if what I'm climbing is too sketchy.

My typical line are extreme structural integrity issues and intense heights. You won't see me walking along a single I-beam with a 100 foot drop below me. I just was never the agile type like that.

I’m with everyone else on the structural integrity... asbestos unless you’re wearing a full hazmat suit you won’t be able to avoid tracking it back into your car etc.. the best thing I do for myself is throw on my p100 and hope for the best like I’m sure everyone else does.

I haven't had an experience like that yet. At least not to an "unexplorable" point. One house i was in was REEKING of what i can assume was raccoon urine. I was basically in their bathroom and it was horrible. Even with a mask on. But it was definitely worth it.