Need to disconnect main vent stack several hours, what to do about fumes/smell ?

If only for a few hours ventilate the area and complete the job.
Why do you have to open it up?
Let me know, Tom

If only for a few hours ventilate the area and complete the job.
Why do you have to open it up?
Let me know, Tom

Thank you for your answer.
Reason is to do framing repairs immediately behind vent which is almost touching a twisted and fire damaged and poorly installed 2x4 in 60 year old cottage/home. I am renovating bathroom and need this framing to be plum and straight to fasten new wall onto, also vent is old cast iron that has copper pipe runs off it, joints are in poor condition as one soldered connection broke apart when tapped on. The soil part of vent has already been replaced with PCV. Installing all new fixtures to update, so will the bathtub need a vent or can it drain OK into main [ seems like it should work ] as it's on it's own drain ?

will the bathtub need a vent or can it drain ok into main
Yes the tub will have to be vented. However if you connect to the lavatory drain line, it will be wet vented.
Good luck Tom