@chazam
180 cubic meters of volume, so 180 x 1000 is 180000 litres of air. Each litre of air has a CO2 concentration of 416 mg/litre.
So 180000 x 0.416 grammes is 74880 grammes of CO2 or 74.88 kg in the room.
Assuming air is dry and cool.
Releasing 2 kg of CO2 from your cylinder into that enclosed space is only going to increase the CO2 from 74.88 to 76.88 ie by about 2.6% overall, or a change of 0.416mg / litre to about 0.4265mg/ litre.
CO2 in the atmosphere has increased from 316 mg / litre in 1959 to 416mg in 2021. So naturally ( thru our actions so not that natural) the CO2 is rising 3x faster year on year than your 2kg escape of CO2.
If it was going to be dangerous for you this CO2 escape you'd be in danger in 4months time from a natural rise in CO2.
This is an approximation, but think it's very ballpark.
If you get the CO2 concentration above 10% in the air then convulsions Coma and death can occur.
1kg of CO2 makes about 554litres of CO2, so 2kg is 1100 litres.
So I think in your sealed dry air cool 180m3 box you'd need 18000 litres of CO2 to get 10% , that would need 16.4 kg of CO2 to be released.
You'll be alright I reckon, however lower concentrations will give air hunger, coordination loss etc.