Submitted by FangNut t3_113ddvc in LifeProTips
With all that is going on with the train derailment in the US, thought it's a good time to push out a gentle reminder for everyone.
We cannot say whether a colourless gas is dangerous or not but any gas with any visible colour is dangerous every single time. This can also be expanded to most cases where there is debris in the air due to incidents such as earthquakes or to cases where there is smoke in the air due to incidents such as fires. Just walk away!
Edit: if it is naturally occurring and you are confident it is safe, the above doesn't apply. If you know it is safe, it's upto you to deem it safe.