[TowerTalk] Stripping rg142

[jimlux]

On 11/25/18 9:54 AM, Patrick Greenlee wrote:
> 
>   "Which is pretty toxic I hear?"
> 
> Which is why when you take a break from tower work to cook a steak (or 
> whatever) you don't get carried away preheating a teflon coated (non 
> stick) pan or you may actually literally get carried away (to the morgue.)
> 
> On 11/25/2018 9:41 AM, Jim W7RY wrote:
>> Yup. Burning teflon produces phosgine gas. Which is pretty toxic I hear?
>> Jim w7ry
>


This is all about risk assessment - which is sort of tower-talk appropriate.

We deal with "potentially lethal substances" all the time.  It's all 
about dose and exposure.

There's also things that are carcinogenic  - which is kind of a 
different concern, because small exposure might cause a problem that's 
not apparent for decades.

But here, we're discussing "acute hazards" - poisonous fumes.

Phosgene (and likely, similar compounds, from decomposition of plastic) 
have LC50 (lethal concentration 50%) in the tens of ppm, for half an 
hour or longer.

the current Permissible Exposure Limit is 0.1 ppm.  It's based on the 
current "Immediately Dangerous to Life or Health" - and those are 
usually set at a level that is around 1/10th of the lowest level at 
which any adverse effect has been noted.

That's 0.4 milligrams/cubic meter.

Looking at the safety aspects - in an industrial setting, you might have 
an exposure that lasts a whole shift (8 hrs), every day.

But how much phosgene are you going to get from melting/burning the 
insulation on a piece of coax. Let's estimate the mass - The insulation 
is probably about 0.1" in diameter, and you're going to burn down maybe 
1 mils of it (most will melt). 2.54mm in diameter * .025 mm long, that's 
about 0.127 cubic mm. Assuming the plastic is 1 g/cc, we're looking at 
0.127 milligrams of plastic that's being destroyed.  There's no oxygen 
in the PTFE, so it picks it up from the atmosphere. I'll just assume 
that the mass doubles to 0.25 mg.

So, to stay below the IDLH level (0.4 mg/cubic meter), you need to have 
at least 1/2 cubic meter or so of air (about 15-20 cubic feet) -   for 
comparison, a bathroom fan is about 50 cfm, as is a typical computer 
cooling fan.

So yeah, you probably don't want to be using the thermal stripper in a 
closed closet.

As for frying pan destruction.. looking online, I find that the coating 
is 1-3 mils (0.0025mm-0.0075mm) and maybe 30 cm in diameter. maybe 1/3 
cc total - Call it 0.5 grams of toxic gases..   That's going to need 
1000 cubic meters to be sufficiently ventilated.. and that's a lot..

Leaving that teflon pan on the stove to burn is really going to be a 
problem.




Your tax dollars provide copious information about these sorts of things:

https://www.cdc.gov/niosh/idlh/75445.html