Hi Katie,
Is it similar to a paraffin smell? If so, the resin is breaking down and I'm afraid that replacing the bricks, elements or stats will not cure the problem. Needs replacing. However, if it's a burnt smell, then replacing the element and bricks will cure the problem.
Regards
Ray

Hi Katie
You have not said what fuel your heaters are but you have done the right thing by turning them off,leave them off until they have been checked by a qualified person,you can call me if needed.

scrap them the elements are deteriating