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BOMI: AHU, WATER TREATMENT & PLUMBING
EXAM LATEST 2025 ACTUAL EXAM| COMPLETE
REAL EXAM QUESTIONS AND CORRECT
VERIFIED ANSWERS/ ALREADY GRADED A+
What is the atmospheric pressure of air at sea level? - ANSWER - At sea level, atmospheric pressure exerts an average force of 14.7 pounds on each square inch of surface (14.7 psi).
Explain Charles' Law. - ANSWER - Charles' law explains why gases expand when heated and contract when cooled. Given a certain quantity of gas, as temperature increases, volume increases. This is because the molecules have the opportunity to move more and spread out. As pressure increases and the volume decreases, the temperature will increase because compressing the gas causes the molecules to vibrate faster and collide into each other more frequently, causing friction heat.
Explain Boyle's Law. - ANSWER - Boyle's law states that at a constant temperature, as the volume increases, the pressure decreases. If the pressure on a certain amount of gas is doubled, the volume of space it requires will be cut in half. As pressure goes up, volume goes down.
How does the human body regulate its temperature? - ANSWER - The body dissipates heat by sending blood from internal organs to the skin where the heat is thrown off into the surroundings by radiant heat loss, convective heat loss, or evaporation. Perspiring and losing the heat through evaporation is an evaporative cooling process and is used in air- conditioning systems as well as human bodies. 1 / 3
pg. 2 What system produces the most heat in a building? - ANSWER - Building lights are the most significant internal heat source. The heat given off by lights depends mainly on the wattage rating of the lighting elements. Lighting systems produce heat loads of up to four watts per square foot. The heat gain from one watt of electrical energy is equivalent to 3.4 Btu per hour.
How have office building AC systems been designed to compensate for heat gain from office equipment? - ANSWER - To compensate for this heat gain from office equipment in modern office buildings, air- conditioning systems have been designed to offset one to three watts per square foot.
What is pull-down load? - ANSWER - Heat left over from the day before must be removed the following morning when the air- conditioning system is restarted. The leftover heat is called the pull- down load and must be added to the instantaneous solar heat gain during the morning hours to determine the cooling load for the air-conditioning system.
How can the problem of air and water vapor infiltration into a building be solved? - ANSWER - To reduce these infiltration problems, ventilation air should be introduced through the air-conditioning system in constant quantities to maintain a slight positive pressure within the building. This pressure causes an outward escape of air through cracks, windows, and doors, limiting infiltration. In this way, the only outside air admitted into the building is that which has been cooled, dehumidified, and cleaned before being introduced into the occupied spaces. 2 / 3
pg. 3 Define absolute pressure - ANSWER - Gauge pressure plus standard pressure gives psia (pounds per square inch absolute), or absolute pressure.
Define static pressure - ANSWER - Static pressure is generally used to describe duct pressure. Static pressure is the pressure of the air being pushed against the inside walls of a closed duct by the fan.
How is velocity pressure calculated? - ANSWER - To measure static pressure, a pitot tube partially filled with fluid is attached at a right angle to a long, straight length of duct. The air entering the tube from the duct will push the fluid inside the tube against the outside air that is used as a reference. The outside tubing allows a measure of the static pressure; the velocity pressure is eliminated from the reading. Velocity pressure is derived by subtracting static pressure from total pressure.
What is pressure drop? - ANSWER - The pressure drop is measured as the difference in pressure between where air enters a device and where it comes out of the device.
What is friction loss? - ANSWER - Friction loss is caused by air molecules slowing down by banging against the surface of the duct interior.
When designing a duct system, what is important to remember about directional changes? - ANSWER - The more changes of direction there are in the duct run, the less direct the airflow will be. Directional changes increase friction and reduce efficiency.
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