Can i use a low voc primer sealer over high voc shellac to lower vocs in the room?

This shouldn't be a problem, I would suggest a zinsser 123 or similar followed by an appropriate undercoat (I would apply 2 coats) to match your topcoat.ie same brand When sanding between coats I would strongly advise the proper PPE in a well ventilated area and would use a fine sanding paper 180 grit to 240 grit or use a dustless system which most decorators would have. Hope this helps with your question and good luck

I wouldn’t use a water based product on top but Would use the low voc primer or zinzzer that woukd stop most things coming through.

Shellac primers use ethanol as a solvent which is why they smell quite strong. However, the fumes of these primers are not toxic and will disappear once the primer is dry. So you don't really need anything on top of that other than your chosen finish coat. You won't have any VOC coming through.

Paints emit Voc's no matter what, some more than others. Keep the area well ventilated for up to 72hrs after application. Always alow the recommended drying times for each application. Most if not all paints / brands have a technical team to talk you through any issues and questions you have. The facility is there to be used , so ask the questions. Shellac will seal old lead paint but be aware it's the sanding of the lead paint without proper PPE or a risk assessment that is the problem. A professional would be wise for this task with all the correct equipment. Hope this helps and stay safe. Regards Scotford Brothers Northampton

You should be able top paint your top coat or coats as the case maybe with satinwood or eggshell finishes