Where should you not use spray foam?

You should not use spray foam in places with existing moisture, near electrical boxes without proper clearance, in areas requiring ventilation, directly against hot surfaces like flues, and in enclosed spaces without proper drying, similar to avoiding improper storage that traps moisture. Do not use spray foam in areas with water leaks or wet wood, as it can trap moisture and cause mold behind foam, requiring dry substrate. Do not use close to knob and tube wiring or old electrical where heat buildup risk, keep 3 inches clearance around electrical boxes per code. Do not use in areas where building needs to breathe, like historic buildings requiring vapor permeability, closed-cell can trap moisture. Do not use directly against chimney flues or hot pipes, need clearance for fire safety. Do not use in areas where future access needed for wiring or plumbing without planning. Do not use open-cell in below-grade or exterior where water exposure, as it absorbs water, closed-cell better for damp areas. Do not use spray foam in attics without proper ventilation or ignition barrier, as it can be fire hazard. Also avoid using in small closed cavities without professional, as over-expansion can damage structure. So avoid spray foam in wet areas, near hot surfaces, over electrical hazards, and where moisture trapping or fire risk exists.