What does the air compressor do with the air it takes in at ambient pressure?
- Filters it to remove impurities
- Forces it into a tighter space ✓
- Heats it to expand the volume
- Cools it to reduce the volume
Answer: B. Forces it into a tighter space
The air compressor forces the air it takes in into a tighter space.
Why this is the answer
The handbook says the compressor draws in air at normal pressure and pushes it into a much smaller space, which raises the air pressure. Another passage describes compression the same way: air is forced into a smaller space. That matches the choice about forcing air into a tighter space. The passages do not describe the compressor as a filter, heater or cooler for the incoming air.
Why the other answers are wrong
- A. Filters it to remove impurities — The passages do not say the compressor filters impurities from the air; an air dryer is mentioned separately to remove moisture.
- C. Heats it to expand the volume — No passage says the compressor heats the air to expand its volume; compression is described as forcing air into less space.
- D. Cools it to reduce the volume — Cooling is mentioned in connection with an air dryer, not as the compressor's way of taking in and compressing air.
Remember it
Picture squeezing air into a smaller container: packing it tighter is what raises the pressure.
Official handbook: Official MTO Air Brake Handbook, Air Supply Subsystem – Air compressor