Asbestos: leave it alone
Asbestos is dangerous when fibers go airborne, which happens when material is disturbed. EPA guidance is that asbestos material in good condition that will not be disturbed should be left alone, and that sampling or removal be done only by trained accredited professionals, because incorrect sampling can be more hazardous than leaving the material alone.
So for intact floor tile, advise leaving it undisturbed. Traps: no rule requires the seller to remove all asbestos before closing; having the buyer sand and seal the tile is exactly the disturbance that releases fibers; and asbestos is not regulated only in commercial buildings.
Mold: moisture and square footage
EPA's mold guidance is about drying and size, not exposure limits:
- materials dried within 24 to 48 hours usually will not grow mold
- areas smaller than about 10 square feet, roughly 3 feet by 3 feet, can be handled by the owner
- keep indoor relative humidity below 60 percent, ideally 30 to 50 percent
The trap you will see most: EPA sets no federal exposure limit for mold or mold spores, so any "federal mold standard" answer is wrong. Also wrong: requiring professional remediation for any visible mold regardless of area, which ignores the size guidance, and keeping humidity above 60 percent, which inverts the advice.
Underground storage tanks
A buried tank is a regulated UST when more than 10 percent of its volume, including piping, is underground. That definitional test is only the first step; the exam rewards going on to the exemptions.
Federal UST rules exempt farm and residential tanks of 1,100 gallons or less storing motor fuel for noncommercial purposes. A 1,000-gallon buried gasoline tank a farmer uses for his own tractors fits. There is a separate real exemption for heating oil stored for consumptive use on the premises, but it is the wrong exemption for a gasoline tank — a true rule applied to the wrong facts. Saying any buried tank is a regulated UST ignores the exemptions entirely.
How these questions are built
Each topic pairs a genuine EPA figure with an invented legal duty. Learn the figures — 24 to 48 hours, 10 square feet, 60 percent, 1,100 gallons, 10 percent underground — and distrust answers where federal law commands rather than recommends.