I'm not sure that's the case,if I'm wrong I apologise but just

what kind of lids you need cause am a noob that all this stuff lol

This is a very similar chamber to mine but I don’t see why you need the overflow hose, in fact I think it will cause you problems. CO2 is very much like water, if you add the dense CO2 in through the top it will build up in the bottom of the chamber and kill the rodents. The air displaced by the CO2 being lighter will float on top of the CO2 and overflow between the top of the box and lid just as water would if you over filled the box.
Also having the overflow pipe fixed low down in the box will mean that you lose the heavier CO2 rather than the air that you are trying to get rid of. Imagine taking the chamber out into the garden and trying to fill it with water. Long before the water gets to the top it will begin running out of the overflow hose, this will also happen to your CO2. Any rodents in the box would be able to reach above the CO2 levels and breath the air above the overflow level, a situation that would prolong the time it takes to kill them and waste lots of your CO2.
I very much doubt that your lid will be air tight but if you feel the air can’t escape around the edges just make a hole in the top of the lid to allow the lighter gas to escape.

Natrix

i'm with natrix on that one... I never had an air pipe or hole in the top of mine and it always worked great...

Also worth noteing is if you plan to cull a lot of mice then for the love of god get yourself a larger cylinder of CO2.. lol.. you can get the big cylinders like they use in pubs from most welding supply places.. there is usually a £10 - 20 deposit on the cylinder but the place i use now charged £15 deposit on the cylinder and the first fill was free (usually costs £10 to fill it up) cant remember of top of my head but i think it might be a 13Kg cylinder.. either way worth a look
Owen

__________________

completely forgot... for the big cylinders you will need a regulator (either pub style one or welding style one). you can pick them up secondhand on ebay, car boot sales, etc usually for £5-20 depending if it is 1 stage or 2 stage and how many gauges it has, etc..

__________________

the over flow is at the top.

The gas is going in through the green tubing, at the side of the tub, and the air flow will go out through the transparent tubing on the top.

Well, that's what it looks like to me anyway

__________________
www.royallymorphedpythons.co.uk

I wasn't sure about the extra tube on the lid either. If C02 is heavy as everyone says it is then the air will get pushed to the top of the chamber regardless of whether there is a tube there or just a vent hole.

Good simple design though. Off to halfords now.

Drew

__________________
A few snakes..
Rotties..
Axolotl..
Mice..

Love the design but my only problem is breeding the mice! It probably wouldn't work for me as the snakes I have and ones I plan to get are all large so they'll all need much bigger than mice! Shame because I love this idea.

Draven

__________________
"It can't rain all the time..."

these are the people we use for the larger bottles they are very good and they deliver to your door

Gas welding, cylinder gases, welding gases - Local UK suppliers of Air Products gases

sorry i havent replied i havent been around for a while.

ye, the green tubing is were the c02 goes into, and the clear tube in the lid is for the air to eascape, if you dont put the hole in the lid will pop open (need to use an air tight lid so that it is as humaine as possible and no air can get in or out) the clear hose then goes into a cup of water, so that no air can go backwards in the hose (mainly for the early stages when only a little co2 is used) so you will be adding the co2 from the green hose in the bottom, the co2 stays at the bottom as it is more dense than air, the air then rises, and is forced out of the clear tube. this leaves the co2 behind but takes out the normal air.

sorry if it was unclear, any questions please just ask