A ventilation fan came on, sucking the blue smoke into the ceiling.

The ventilation fans were roaring but the air was hot and foul.

Maybe the doctor would have a nice, noisy ventilation fan.

Then he realized suddenly that it was simply a ventilation fan.

From behind it, she heard the hum of the ventilation fan.

That one was for ventilation fans if the natural circulation couldn't cope with smoke or gas.

He had some crew members turn on ventilation fans.

They could have used it to shut down the ventilation fans and inhibit the flow of gas.

Despite the hum of her ventilation fan, Laurie could hear whistling.

Return air is extracted by ventilation fans mounted on the surface.