Ahh with welding, you need to be working in a well ventilated area.

I use a household fan and have it blowing on the work area to clear the fumes.

The gasses released from welding are not very good for you and should be avoided.

As far as using a respirator, well you have to remember that there are different types of filters available, and that you need to use the right one for the right job.

Eg a P3 type filter is fine for the paint dust, but will not protect you against the fumes. You wil need to use an organic type filter in conjunction with a P3 for proper protection.

PPE is not as simple in reality unfortunatly.