Carbon dioxide is like nitrogen in many ways, but if it is mixed with limewater, it causes the clear liquid to because milky, while nitrogen dose not. This is the test for carbon dioxide.

Test smoke, carbon monoxide and security alarms to make certain they work it’s a good idea to replace batteries even if they are still working.

Alarms. Test smoke, carbon monoxide and security alarms to make certain they work it's a good idea to replace batteries even if they are still working.