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Thread: Minimizing exposure to chemical coatings used in tents

  1. #1 Minimizing exposure to chemical coatings used in tents 
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    Hi, my family often goes hiking and we use backpacking tents,
    I've recently been reading that pretty much all tents sold in the US are coated with flame retardants and with fluorocarbons (these act as a DWR - durable water repllent).
    I've also been reading that these are not excatly chemicals you want to expose yourself and your children too, not to mention the environment.
    But as far as it seems there is no real alternative at this point and pretty much all companies use these materials.

    I'd like to ask if you know much about these chemical compounds and could advise me on reducing exposure to them, the exposure would probably be either airborne or by physical contact with the fabrics coated with these chemicals.


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  3. #2  
    Bullshit Intolerant PhDemon's Avatar
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    I don't know a great deal about these types of compounds but from my perspective as a chemist I can give the following advice/information

    As for personal exposure:


    As far as airborne exposure goes a good indication for most things is "can you smell it?" (although I know some things have no odour a lot of organic compounds of this type do). If you can't they are probably involatile enough not to be airborne and I wouldn't worry too much unless you are cutting the material and creating dust particles containing them that could be inhaled. (If you want to quantify this you could look up the vapour pressures (which may be on the MSDS and calculate the mass flux of the compound from the material).

    As for physical contact that is a trickier one. I'm guessing if they are being used commercially they are either not absorbed through the skin (or if they are have been shown to be harmless in toxicology studies -- for this information look up the MSDS for the specific compounds, it will have all the data that is available/relevant). To minimize exposure the obvious thing is to spend as little time as possible in the tent! I can't think of any other way...

    As for environmental impacts without information on the type of flame retardant I can't really comment, for fluorocarbons, one type of this type of compound, CFCs (in the lab we called them "ozone f***ers") were the cause of the stratospheric ozone hole. These are now no longer allowed to be used, what are now used are HFCs which react chemically (primarily with OH) in the troposphere and do not reach the stratosphere where they can be photolysed and so do not affect the ozone layer (although some of them do have quite long lifetimes). They do act as greenhouse gases though, they have global warming potentials of ~100~1000 times that of CO2 (but the much lower concentrations mean there impact is less important) so environmental release of these compounds is not a good thing...


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  4. #3  
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    Quote Originally Posted by fiftyeight58 View Post
    Hi, my family often goes hiking and we use backpacking tents,
    I've recently been reading that pretty much all tents sold in the US are coated with flame retardants and with fluorocarbons (these act as a DWR - durable water repllent).
    I've also been reading that these are not excatly chemicals you want to expose yourself and your children too, not to mention the environment.
    But as far as it seems there is no real alternative at this point and pretty much all companies use these materials.

    I'd like to ask if you know much about these chemical compounds and could advise me on reducing exposure to them, the exposure would probably be either airborne or by physical contact with the fabrics coated with these chemicals.
    I'm not expert on this but reading on the web it seems the known problems are mainly associated with perfluoro-octyl sulphonate (PFOS) and perfluoro-octanoic acid (PFOA) and that for that reason these have now mostly been superseded by shorter chain perfluoro compounds that bioaccumulate less easily. I did notice a company called Nikwax fairly aggressively promoting itself as NOT using this type of water repellant and there do seem to be some others.

    These sites seemed informative, though the 2 commercial ones are obviously promoting a particular point of view for their products.

    Perfluorinated compound - Wikipedia, the free encyclopedia

    https://www.nikwax.com/en-gb/environ...nvironment.php

    http://www.grangers.co.uk/downloadar...ct%20sheet.pdf
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  5. #4  
    Time Lord
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    Thanks for bringing this up fiftyeight58. That "new tent smell" can be rather heady, yet I hadn't thought about it.

    Maybe pitch your tent in the garage for a month before camping.
    A pong by any other name is still a pong. -williampinn
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  6. #5  
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    Yes, there is certainly a smell to new tents, hard to tell of it comes from one of the hazardous compounds we were talking about.

    Also PhDemon, I saw your comment about calculating the mass flux, I do not know how to do this, and if I did, would not be sure how to interpret the result. Could you maybe give more information of this?

    Thank you guys
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  7. #6  
    Bullshit Intolerant PhDemon's Avatar
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    To calculate the mass flux from the surface I would use the Langmuir equation:



    where is the rate of mass loss from the surface per unit area, M is the molecular mass of the evaporating species, k is Boltzmann constant, T is the temperature (in Kelvin), P* is the saturation vapour pressure of the evaporating species and P is it's partial pressure in ambient air (in most cases ~0).
    If you do this calculation (using SI units ) you will calculate how much of the stuff is evaporating in kg per square meter per second.

    Although this strictly only applies to the evaporation of liquid (IIRC) IMO it will give you a reasonable estimate of the of the evaporation rate (which I'm guessing will be slow) as long as the coating is uniform and covers the whole surface.

    If you are interested it is derived here: Langmuir’s Equation for Evaporation | Jun's Notes

    (and I note they assume the ambient partial pressure is zero so only the saturation vapour pressure is included in the equation).
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