Free ASCS Practice Questions

Question 1

Before agitation begins in a long supply run, pressure at the collection-hose connection is strongly negative relative to the room. A manometer at the far branch shows no pressure difference. The collector is at full output, and intervening dampers are open. What setup change addresses the unprotected branch?

Accepted Answer

Isolate a shorter duct section, move suction closer, and verify negative pressure before agitating.

Answer

Open more supply outlets to increase make-up airflow through the duct.

Answer

Add a room HEPA scrubber without changing the duct-collection arrangement.

Answer

Increase compressed-air pressure to drive debris from the far branch toward the collector.

Question 2

A homeowner reports that dust has returned soon after HVAC cleaning. Inspection finds fresh streaks immediately downstream of gaps around the filter frame; the filter media is intact and the return-duct joints are sealed. Which recommendation best addresses the observed contamination pathway?

Accepted Answer

Correct the filter fit and seal the bypass gaps.

Answer

Install higher-MERV media in the same rack without changing the filter fit.

Answer

Shorten the duct-cleaning interval so deposits are removed before they can spread.

Answer

Replace the filters more frequently to prevent loading of the existing media.

Question 3

A cooling-only VAV terminal delivers its scheduled minimum airflow when the room is at setpoint and rises smoothly to scheduled maximum flow when cooling demand increases. The duct and coil surfaces are clean. The owner wants the damper locked open to prevent low airflow. The ASCS should recommend:

Accepted Answer

Keep the scheduled settings; the measured response is normal VAV operation.

Answer

Increase minimum flow until the terminal stays near maximum delivery.

Answer

Remove the terminal from service until its actuator has been replaced and recalibrated.

Answer

Reclean the branch before accepting reduced airflow as normal operation.

Question 4

After cleaning, two separately isolated bare-metal duct sections receive valid NADCA Vacuum Tests at the agreed representative locations, before system restart. East yields 0.30 mg/100 cm²; West yields 1.10 mg/100 cm². Their average is 0.70 mg/100 cm². The contract requires each section to meet the NADCA criterion. Which acceptance decision follows?

Accepted Answer

Accept East; reclean and reverify West before accepting that section.

Answer

Accept both sections using the 0.70 mg/100 cm² average.

Answer

Require both isolated sections to be recleaned and retested because one exceeded the limit.

Answer

Accept West if its airborne particle count is lower than the surrounding room count.

Question 5

During an AHU assessment, a small quantity of test water remains in the condensate pan with the fan running but drains immediately when the fan stops. The fan is downstream of the coil, cooling is disabled, and the pan is properly sloped. The drain outlet and piping beyond the trap are clear. What is the most likely cause?

Accepted Answer

An inadequate condensate trap for the cabinet's negative pressure.

Answer

An undersized condensate drain line.

Answer

A pan pitched away from the condensate outlet.

Answer

Excess outside-air moisture condensing on the cooling coil during the test.

Question 6

A contractor has a fiberglass-compatibility letter and an SDS for an EPA-registered biocide labeled only for unlined metal HVAC surfaces. For a home's fiberglass-lined ducts, what is the compliant application decision?

Accepted Answer

Do not apply it to the liner; the registered label excludes that use.

Answer

Use it after a small test patch confirms that the facing is not damaged.

Answer

Use it with owner consent if the SDS lists no special respiratory hazards.

Answer

Use the labeled dilution with a longer ventilation period before the system restarts.

Question 7

Loose surface dust is the only defect on a dry, intact fiberglass sound attenuator. The manufacturer's instructions permit contact cleaning. Choose the appropriate work method.

Accepted Answer

Use a soft-bristle nozzle and gentle HEPA contact vacuuming; preserve the sound facing.

Answer

Replace the attenuator rather than disturb its fibrous acoustic surfaces.

Answer

Wet-clean the facing, then use the collection system to accelerate drying before restarting the AHU.

Answer

Coat the dusty facing to bind particles before any contact cleaning.

Question 8

Before coil cleaning, an AHU fan draws 5.0 kW while delivering 10,000 cfm. The first post-cleaning reading is 2.3 kW at 8,000 cfm. After airflow is restored to 10,000 cfm under comparable operating conditions, input is 4.5 kW. The facility expects 2,000 annual operating hours at 10,000 cfm. What annual fan-energy reduction should be reported?

Accepted Answer

1,000 kWh, using the power reduction at matched airflow.

Answer

5,400 kWh, using the lowest post-cleaning power reading.

Answer

9,000 kWh, representing total post-cleaning fan consumption at restored airflow.

Answer

1,111 kWh, applying an 11.1% reduction to the original annual fan consumption.

Question 9

During HVAC cleaning in an occupied office, two workers and a receptionist develop headache and nausea. A gasoline-powered generator is operating outside near an outdoor-air intake. The supervisor suggests checking the collector's HEPA filters before interrupting work. Which response takes priority?

Accepted Answer

Evacuate everyone to fresh air away from exhaust and call emergency services.

Answer

Measure CO at the registers before ordering an evacuation.

Answer

Shut down the generator and have occupants wait indoors while the air handler purges the building.

Answer

Relocate symptomatic people to another room and run additional HEPA scrubbers.

Question 10

A multirow cooling coil has sound fins and no corrosion. Type 1 dry cleaning removes the face dust, but inspection still shows packed debris between the coil rows. Both sides are accessible and the manufacturer permits wet cleaning. Under ACR 2025, what should the crew do next?

Accepted Answer

Perform Type 2 wet cleaning, controlling rinse water to protect adjacent components.

Answer

Repeat Type 1 cleaning at higher compressed-air pressure.

Answer

Replace the coil because the dry-cleaning attempt left debris between its rows.

Answer

Apply an antimicrobial, then accept the coil once readings show that the design airflow has returned.

Free ASCS Practice Questions

Domain 1: Benefits of HVAC System Cleaning 16% of exam

Question 1

Question 2

Domain 2: Mechanical Systems 15% of exam

Question 3

Domain 3: Understanding Assessments 12% of exam

Question 4

Domain 4: Cleaning and Restoration Procedures 42% of exam

Question 5

Question 6

Question 7

Question 8

Domain 5: Health & Safety of Employees and Building Occupants 7% of exam

Question 9

Domain 6: Standards & Guidelines 8% of exam

Question 10

That's 10 of 1,030