Room-conditions supercritical fluids?

Are there any reasonably obtainable supercritical fluids that I could, say, run my hand through? Wikipedia makes it sound like there are plenty of room-temperature ones, but no room-*pressure* fluids.




As you can see on this [data page on Wikipedia](https://en.wikipedia.org/wiki/Critical_points_of_the_elements_%28data_page%29) helium-4 has critical pressure of 2.24 atm, but helium-3 has 1.13 atm, only slightly above atmospheric pressure. [Hyperbaric chambers](https://en.wikipedia.org/wiki/Hyperbaric_medicine#Hyperbaric_chambers) work with 1,3-1,5 atm, so you could try there.


There is, unfortunately, question if it has sense, as you wouldn't notice any serious difference in properties between subcritical helium-3 and slightly above critical point in pressure, but so far above in temperature. It would still be lighter than air, for example.


I don't think that much higher pressure would be a huge problem - the highest pressure survived by human is supposedly 54 atm - so says [Wikipedia](https://en.wikipedia.org/wiki/Ambient_pressure), but I didn't find proof. If there is a compound with critical parameters sufficiently near standard, you could touch liquid-like, not gas-like supercritical fluid.


Ionic liquids have relatively low critical pressures (even only 14 bar), but too high crit. temps ([source](http://pubs.acs.org/doi/pdf/10.1021/ie0603058)). On the other hand ethane's crit. temp. is below 30°C, but pressure over 48 atm. Maybe there's sweet spot somewhere, but it would be still high pressure and may be quite hot or cold.


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A number of long carbon chain molecules with large numbers of fluoride atom, have $P\_c < \pu{10 atm}$ and $T\_c < \pu{1000 K}$. That is within the reach of a good bicycle pump and a burner. In particular [$\ce{C12F26}$](https://www.chemeo.com/cid/10-804-7/n-Perfluorododecane), [$\ce{C15H4F28O}$](https://www.chemeo.com/cid/75-143-0/1H,1H,15H-Octacosafluoro-1-pentadecanol.pdf) and [$\ce{C20F42}$](https://www.chemeo.com/cid/12-080-9/Perfluoroeicosane): 


\begin{array}{lll}
&\ce{C12F26} &P\_c = \pu{912 kPa} &T\_c = \pu{417 K} \\ 
&\ce{C15H4F28O} &P\_c = \pu{784 kPa} &T\_c = \pu{701 K} \\
&\ce{C20F42} &P\_c = \pu{463 kPa} &T\_c = \pu{700 K}
\end{array}


The critical point of a fluid is determined by its van der Waals constants.
For a fluid to be critical at STP it needs these constants to have the values
$a = 25$ and $b = 0.003$ in SI units. The value of $b$ corresponds to a molecule with around 300 atoms, but the value of $a$ is outside the range of published compounds.


However, something compounds like $\ce{C100F202}$ could be critical at around ordinary pressure and an easily achievable temperature, i.e. it might be possible to get a critical fluid by heating some goop in an open saucepan. 
It also seems that fluorocarbons tend to be stable and inert, so they may be safe enough to handle.


@Diracology and @Floris provide an in depth exposition of the relationship between critical points and van der Waals constants in their answers to my Physics.SE question [Fluids with critical point at ordinary temperature and pressure](https://physics.stackexchange.com/questions/268470/fluids-with-critical-point-at-ordinary-temperature-and-pressure). Their answers with internet search of van der Waals constant data lead me to start looking at at large fluoroacarbons. The ones listed above are the largest I could find data for. It should be possible design more suitable molecules computationally. See [Computing van der Waals constants from molecular structure](https://chemistry.stackexchange.com/questions/55784/computing-van-der-waals-constants-from-molecular-structure).


 6

If exceeding the "[liquid–liquid critical point](https://en.wikipedia.org/wiki/Critical_point_(thermodynamics)#Mixtures:_liquid.E2.80.93liquid_critical_point)" for a solution suffices, then perhaps you could survive contact with [methane hydrate](http://petrowiki.org/Equilibrium_of_water_and_hydrocarbon_systems_with_hydrates) for a short while. Though He is supercritical at ~two atmospheres, running you hand through it would be a chilly experience at about 5 K.


 5

Quick googling got me to $\ce{CF3Cl}$, that has cr.p. at $\pu{28.8^\circ C}$ / $\pu{38.6 bar}$. $\ce{C1}$-$\ce{C2}$ freons look to have critical point in $\pu{30 .. 60 bar}$ / $\pu{0 .. 100^\circ C}$ range, so some of them probably are survivable. However, some compounds of this class are used for general anesthesia, so $\ce{He/O2}$ mixture respirator would be required.


 5