Best Strongest Rechargeable Batteries Gas When Recharging Non-rechargeable Batteries?

Gas when recharging non-rechargeable batteries? - best strongest rechargeable batteries

Read E is a simple email my friend told me that her roommate tried to not re-charging rechargeable at home today and now there is a strong smell of gas.

What is the gas to radiate it? What would have happened if he had left the office? And above all, it is harmful? Thanks