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My desktop computer system employs a liquid cooling loop featuring a 6-litre external reservoir and radiator combination "cooling tower" unit. It isn't a cooling tower in the strict sense as it does not achieve temperature reduction through any evaporative method - only by radiating heat through the metal structure. However, the reservoir is not sealed and I have noticed a reduction in the level of liquid over the past few months since I started using it - I must assume that I'm breathing-in this liquid in some amount.

The coolant used describes itself as:

XSPC EC6 is a high performance, eco-friendly coolant for PC water-cooling. It’s based on a blend of refined vegetable extracts with non-toxic corrosion inhibitors and non-toxic dyes. It offers superb protection for copper, brass, steel, nickel, aluminium and has been tested with a range of acetal and acrylic plastics

Never one to trust marketing materials, I requested a material safety data sheet from the manufacturers, and details of the ingredients. I only received an MSDS back without an ingredients listing. The MSDS reports the following:

COMPOSITION / INFORMATION ON PRODUCT COMPONENTS
Hazardous Components for EC
Low oral toxicity proprietary antifreeze formulation based on refined vegetable extracts and non-toxic corrosion and scale inhibitors. Classified as GRAS (Generally Regarded as Safe) as a food additive and not classified as harmful for handling or transport purposes. However we recommend good working practices are employed and personal protection gear is worn when handling any chemical.

[...]

EXPOSURE CONTROL/PERSONAL PROTECTION
Respiratory Protection: Respiratory protection if there is a risk of exposure to high vapour concentrations.

[...]

TOXICOLOGICAL INFORMATION
Acute Toxicity: LD 50/oral/rat: >20000 mg/kg

[...]

ECOLOGICAL INFORMATION
Mobility: The product will dissolve rapidly in water. Ecotoxicity: The product is rated as:
Algae EC50 (72h):>100mg/l.
Fish : LC50 (96h):.100mg/l, Oncorhynchus mykiss
Bacteria: >1000 mg/l Daphnids (acute) EC50 (48h):>100mg/l

My guess is that it's some glycol-based solution - I'm disappointed they don't reveal the actual ingredients.

Is this substance anything I should be concerned about? Is there any carcinogenic potential?

Also, how can I determine the specific heat capacity of the coolant? As it is used in a reservoir system instead of an active heat-exchange system the heat-capacity is important - I would like to be able to calculate exactly what TDP (Thermal Design Power) computer components I can use and how long I can run them for at-load without fear of overloading the cooling system.

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    $\begingroup$ Unfortunately, it is a rather common practise to keep the actual composition of formulations a secret. However, I doubt that ethylen glycol is a major component in the mixture. I'd rather assume that it contains 1,2-propanediol and 1,2,3-propanetriol, which are both much less toxic that ethylene glycol. $\endgroup$ – Klaus-Dieter Warzecha May 14 '16 at 13:52
  • $\begingroup$ @KlausWarzecha Those substances seem safe - though the docs state it produces acrolein "when heated" - the temperature of the coolant in operation is about 35-40 degrees Celsius - does that constitute "heating" and is that hot enough to produce acrolein? $\endgroup$ – Dai May 14 '16 at 22:03
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    $\begingroup$ I do not expect that acrolein is formed at temperatures around 35-40 °C. Classical catalytical transformations of glygerol to acrolein were gas phase reactions using aluminium oxide or silicon oxide catalysts and temperatures in the range of 180-350 °C. Your computer will hopefully never reach these temperatures ;-) $\endgroup$ – Klaus-Dieter Warzecha May 15 '16 at 5:49
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It can never be said that you are "safe" from any chemical until you find out what the fluid is.

My money is on it being a variant of propylene glycol with merely some dye and that they're trying to play the "secret unique recipe" card. Its an easy way to up-charge on a super useful and cheap product. You also said "a small container over a few months", correct? If so, I believe at that rate of evaporation, you're probably safe. I'm sure exposure to a fog machine in a "club" would expose you to more glycol.

If your really worried and need to get the info, you can play a slightly deceptive and (some would say) unethical trick. Call they're 800 number on the back of they're packaging and say some of their fluid spilled in (x) family members eye and you're taking them to the hospital. Say you've been flushing the eyes with water and need to know the primary or any toxic chemicals in the reservoir.

--- This situation above is completely hypothetical of course.

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    $\begingroup$ Heh. Very nice, but there's no guarantee they'll actually tell you what's in it: They may just give you a spiel of something to tell the doctor and how to flush the eye properly. $\endgroup$ – orlando marinella Jun 14 '16 at 12:32
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General common sense should always remind you not to drink the liquid stick your finger in it, rub it all over your skin or breathe its vapours for extended periods of time. Paracelsus is best known in Germany for this quote:

All things are poison and nothing is without poison; only the dose allows that a thing is not a poison.

If you are now scared out of your wits, then please relax and consider that preface a general disclaimer. Because all the toxicologic data I can see points towards the liquid being entirely harmless. Here’s why:

  • Acute Toxicity: LD 50/oral/rat: >20000 mg/kg

    That’s more than $20~\mathrm{g/kg}$ — an incredible number for $\mathrm{LD_{50}}$ values. Usually, the highest $\mathrm{LD_{50}}$ values I see are $2~\mathrm{g/kg}$. And the greater than basically means ‘we couldn’t kill the rats with that oral dose so we gave up.’

  • Low oral toxicity proprietary antifreeze formulation based on refined vegetable extracts and non-toxic corrosion and scale inhibitors. Classified as GRAS (Generally Regarded as Safe) as a food additive and not classified as harmful for handling or transport purposes. However we recommend good working practices are employed and personal protection gear is worn when handling any chemical.

    (Emphases mine) As you can see, there are numerous references to ‘nope, this thing really won’t harm you.’ The GRAS classification actually seems to be concerning food additives. No danger here.

  • Respiratory Protection: Respiratory protection if there is a risk of exposure to high vapour concentrations.

    I’ll admit, this sounds a tad unsafe at first glance. But if you know what MSDS write for truly unsafe compounds, you’ll realise that this is saying ‘If we write “safe”, somebody will stick their nose in, suffocate and then sue us, so we have to put some kind of caveat here.’

The only thing that actually hints at a potentially harmful substance is the thing about high vapour concentrations. But remember that this is a cooling liquid; you don’t want a cooling liquid evaporating away, that would reduce the cooling efficacy. The minute amounts you are losing will dilute well in the air in your room. Open the window once a day or every two days and you’ll have removed anything that can potentially harm you. The liquid is as safe as it gets.

However, don’t sue me if you decide to turn off common sense and start drinking the liquid or stop venting your room or whatnot.

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