In a structure fire with a single open doorway, the _____ is the lower portion of the doorway.

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Multiple Choice

In a structure fire with a single open doorway, the _____ is the lower portion of the doorway.

The moving air in a structure fire with an open doorway follows a bottom-in, top-out pattern. The fire consumes oxygen and the hot gases rise, so cooler outside air is drawn into the building through the lower portion of the doorway. That lower portion is the air intake, supplying the oxygen the fire needs to keep burning. The hot smoke and combustion products exit mainly through the upper portion, which acts as the exhaust path. The neutral plane refers to the height within the opening where inflow and outflow meet and can shift with fire conditions; it’s not simply the lower part. A high pressure area isn’t the standard label for this flow pattern.

The moving air in a structure fire with an open doorway follows a bottom-in, top-out pattern. The fire consumes oxygen and the hot gases rise, so cooler outside air is drawn into the building through the lower portion of the doorway. That lower portion is the air intake, supplying the oxygen the fire needs to keep burning. The hot smoke and combustion products exit mainly through the upper portion, which acts as the exhaust path. The neutral plane refers to the height within the opening where inflow and outflow meet and can shift with fire conditions; it’s not simply the lower part. A high pressure area isn’t the standard label for this flow pattern.

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