I've had a couple of guys in my house today to replace an old aircon unit.

They started by letting out the gas.

Then they replaced the unit, refilled it from a tank. Seemed to have some problems, emptied it again, refilled it again.. maybe 4-5 times.

All of that gas went psst out in the air.

I was trying to find out if this is freon, they "mei lou".

Anyone know if they still use freon for AC units here?

PS. Not sure if this is the right section, seemed most appropriate...

Yes, older air conditioners still use either Freon R-12 (autos) or R-22 & R-502(refrigerators, air conditioners, etc.). The common term "Freon" is actually a Dupont trademark for R12 & R22 which is a CFC' (ChloroFluoroCarbon) gas.

Many countries have banned production of R12, R22 and R-502, as they contribute to the depletion of the earth's ozone shield. These same countries also require the CFC gases be recovered before items containing same, are discarded. (Recovered gases are processed, cleaned and used again to recharge older refrigeration units.)

Newer cooling systems use replacement gases such as R4-10a and R134a, which also have environmental concerns, such as contributing to global warming.

From your description, it sounds like the service people may have had a "freeze-up" problem, caused by moisture in the cooling lines. A freeze-up will prevent circulation of the "freon" gas, which has been compressed into a liquid, and therefore, little or no cooling.

Proper recharging of any "freon" refrigeration unit involves replacement of the systems "dryer" unit (which absorbs moisture) and evacuation of all air in the system using a vaccum pump. All this prior to recharging. Failure to follow these basic proceedures may reduce overall cooling capacity of the system and could result in premature failure of the systems compressor.

It was a brand new system I had installed replacing an old one.

I was just a bit surprised, to say the least, of the way they were just letting all those gasses out after so many years of having been told of the damages those CFC gasses do the environment.

But I guess I shouldn't have been surprised. TIT afterall, and "everybody does it".