Question

an oil furnace in a garage should not have a buried oil tank requires an outdoor combustion air intake should be installed at least 18 inches above the floor level should not be used in a garage with an interior drain for fear of oil leakage into the drainage system should have 18 - inch clearance from combustibles on all sides question 32 draping of concrete garage floors is usually caused by slab settlement at perimeter concrete shrinkage water absorption and subsequent freezing too much water in the concrete mix missing or undersized rebar

Explanation:

For the oil - furnace question, safety codes often require oil furnaces in garages to be installed at least 18 inches above the floor level to prevent ignition of flammable vapors. For the concrete - floor question, slab settlement at the perimeter can cause the draping or sagging of concrete garage floors as the edges of the slab drop relative to the center.
For the first question about the oil furnace, having a buried oil tank is not an absolute prohibition, an outdoor combustion air intake is not always a strict requirement for all set - ups, using in a garage with an interior drain is not always prohibited with proper safeguards, and 18 - inch clearance from combustibles is not the most defining characteristic compared to the height requirement. For the second question, concrete shrinkage usually causes cracking rather than draping, water absorption and freezing cause spalling, too much water in the mix causes weakening and cracking, and missing or undersized rebar causes cracking and structural issues rather than draping.

Answer:

1. should be installed at least 18 inches above the floor level
2. slab settlement at perimeter