Any methods to cover yourself when dealing with smell during repair
In your case a fully isolating mask connected to some source of fresh air is the best solution. Perhaps you could get without a tank and just have two pipes that end somewhere where there's no substance you protect from - not sure if it works, but worth considering.

The problem with the mask is it has pretty limited blocking capacity - if the substance has high concentration the mask filter will get saturated pretty soon and the mask will get ineffective. Add to this that it complicates breath and it's clear that the mask is not always the best option.