I always though CO was painless if done correctly,
CO and even CO2 are painless in very high concentrations, actually. (Because you go unconscious before the unpleasant symptoms of those gases kick in.) In lower concentrations that you'd get from charcoal or car exhaust (without a catalytic converter) or common sources of CO/CO2 for suicide, it can be mildly to extremely unpleasant - with a decent concentration of CO, you will die, but will probably experience mild discomfort and a bit of a headache first, with CO2 in lower concentrations, you trigger the hypercapnic response and get the panicy sensation of suffocating to death, which is quite unpleasant. You generally don't find CO or CO2 in sufficient concentrations for a painless death, though it is possible to get both in high purity through industrial gas suppliers. But why bother if you can get a safer inert gas cheaper?
also i imagine Nitrogen to be painless as well, however there runs a concern with how much is enough 40 minutes is allot, is a standard 60Cuft tank enough to run 40 minutes.
So, the oft quoted 40 minutes figure is from the longest observed time to death using inert gas, back when the method was new and they were generally using masks rather than plastic bags. Masks almost never fit quite right or maintain a proper seal, leading to leakage, meaning a higher gas quantity expended and low concentrations of oxygen (probably) being inhaled to slow death down a bit. Generally, time needed to irreversible brain death with total hypoxia is 20 minutes, call it 30 to be safe, and 40 to be paranoid. If you don't mind being in a permanent vegetative state, 10 minutes should get you there, but that's not exactly recommended, for obvious reasons. (Not ideal, but I'd take it over being alive - as far as I'm concerned, once my brain goes, I'm gone too, if someone wants to hook my living dead body up to life support, I sure won't know or care, but that's more a personal philosophy thing.)
The original helium method used one or two 4.9 cu ft helium tanks, and the advice was that one should do, but use two to be safe, provided you can hook both up properly - some sources even recomended sticking to just one of those small tanks because of the large number of issues with the T junction connecting the two canisters leaking. The smallest industrial inert gas tank I've seen (in the US, anyway) is 20 cu ft, twice the volume of of the recommended helium tanks, back in the days before helium was widely adulterated with oxygen. Industrial gas containers are also compressed at higher pressures than disposable helium tanks used for blowing up party balloons, so you actually end up with a fair bit more gas than you'd find in an equal volume of disposable helium party balloons, meaning the "small" 20 cu ft nitrogen tank should be plenty... not that it can hurt to have more than you need. More gas means a higher flow rate is possible, so you give yourself plenty of time to die, while pumping enough gas into the bag that you'll be breathing pure, fresh nitrogen the whole time, no worries about the hypercapnic response or low concentrations of oxygen entering the bag and keeping you alive a little longer.
In any event, you should test. Always test, always practice (well, to the extent you can without risking an early bus ride).
I am sure people here have read the report on the european man connecting a nitrogen tank to a full face diving mask with regulator. any thoughts?
Less reliable than an exit bag, and way more expensive. If you have a lot of SCUBA or other airtight, full face mask experience, you can probably make it work reliably, but why bother? You can put together a reliable exit bag anyone can work flawlessly for under $10, or spend hundreds of dollars on an airtight full face mask and figure out how to use it. No brainer.
Who knows
