ICC Commercial Mechanical Practice Exam

Which part of the area must an exhaust system move air across for gases having a vapor density less than air?

1. floor

2. ceiling

3. interior

4. exterior

The correct answer is: ceiling

The correct answer relates to the principle that gases with a vapor density less than air will rise. Therefore, an exhaust system designed to move such gases must operate at the ceiling level, where the lighter gases accumulate. When dealing with exhaust systems in commercial settings, it's crucial to ensure that they are installed in locations that effectively capture and remove these lighter gases from the space. Placing the exhaust system at the ceiling allows it to efficiently vent these gases before they have a chance to disperse throughout the room. Choosing the ceiling as the location for the exhaust system also corresponds with designing for safety and health standards in mechanical systems. This ensures that potentially harmful gases are expelled outside effectively and maintain indoor air quality.