a surgical air vacuum apparatus includes an air pump disposed in a primary air channel for moving air between an inlet port and an outlet port of the vacuum . the air pump has properties for generating heat while moving the air , and the moving air has characteristics for cooling the pump . an air filter disposed in the primary channel has a tendency to block the air that would otherwise cool the air pump . means is provided for combining a secondary air channel and the primary air channel along at least one passage to introduce bleed air to the pump when the filter blocks the primary channel .