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NATE_AIRDIST_SERVICE NEC 2023

NATE Air Distribution Service Practice Test 2

This test focuses on CFM and airflow measurement: the difference between CFM and static pressure, using a flow hood and an anemometer, and how airflow changes with restrictions like a dirty filter or dirty coil.

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NATE Air Distribution Service

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Frequently Asked Questions

Yes — completely free with no signup required. Every question includes a full explanation of the correct answer.

Two: the NATE Core exam plus at least one specialty exam (for example AC Service, Heat Pump Service, or Air Distribution Service). You can take them on the same day or separately.

The Core exam has 50 questions and each installation or service specialty exam has 100 questions. You need 70% on each to pass — 35 of 50 on Core and 70 of 100 on a specialty. Check natex.org for the current format before you book.

NATE certification lasts two years. To renew, you submit 16 hours of continuing education or retake the specialty exam before your certification expires.

No. These are independent practice tests written to match the published NATE exam topics. They are not official NATE exam questions.

Exam Tip: Remember that CFM is the actual volume of air moved, while static pressure is the resistance to that flow. They are related, but they are not the same measurement.

30

Questions

30 min

Time

70%

Pass

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NATE Air Distribution Service Practice Test 2 — Question List

Question 1: CFM is a measurement of what?

The volume of air moved per minute
The resistance to airflow in a duct
The refrigerant flow rate in the lineset
The voltage supplied to the blower motor

Question 2: Which tool directly measures actual CFM at a supply register?

Manometer
Flow hood
Clamp meter
Refractometer

Question 3: An anemometer is best described as a tool that measures what?

Static pressure inside the plenum
Refrigerant subcooling
Air velocity, such as at a register or grille
Electrical current draw

Question 4: Why is it important to distinguish CFM from static pressure?

They are always equal in a properly designed system
CFM is only used in heating mode
Static pressure is only used in cooling mode
They measure different things, so a technician needs both to fully understand airflow performance

Question 5: A technician measures static pressure and finds it is within the equipment's rated value, but a flow hood shows low CFM at several registers. What should the technician suspect?

Something is restricting airflow to those specific registers, such as crushed flex duct or a closed branch damper, even though overall system static pressure looks acceptable
The flow hood must be broken since static pressure is normal
Low CFM at a register always means the refrigerant charge is low
This combination is impossible and cannot occur

Question 6: True or False: Higher resistance in a duct system generally reduces CFM for a given blower speed.

False, resistance and CFM are unrelated
True
False, higher resistance always increases CFM
True, but only for gas furnaces

Question 7: When using a flow hood to check airflow across a home, what is the technician most directly trying to confirm?

The refrigerant charge at the outdoor unit
The voltage at the disconnect
That each register is delivering its designed CFM
The gas pressure at the manifold

Question 8: A technician wants to estimate CFM at a register using an anemometer instead of a flow hood. What additional information is needed?

The refrigerant type used in the system
The thermostat setpoint
The blower motor's horsepower rating
The register's free area (effective opening size), so velocity can be converted into an airflow volume

Question 9: A homeowner complains a room is not cooling well. The technician measures low CFM at that room's register. Which of these is a plausible cause?

Crushed or kinked flexible duct feeding that register
The outdoor unit's disconnect is in the off position
The condensate drain line is clogged
The thermostat batteries are low

Question 10: What does design airflow (CFM) for a room usually depend on?

The color of the register grille
The room's heating and cooling load, calculated during system design
The brand of thermostat installed
The homeowner's personal preference alone, with no calculation involved

Question 11: A technician notices the blower is running at the correct speed, static pressure is close to rated, but total system CFM still seems low. What should be checked next?

The color of the duct insulation
The brand of the thermostat
Whether the duct system itself (leaks, undersized runs) is preventing air from actually reaching the registers
The refrigerant type used in the system

Question 12: A manometer reading alone can tell a technician what, without a separate airflow measurement?

The exact CFM at every register
The refrigerant charge level
The exact temperature split across the coil
How much resistance to airflow exists, but not the exact CFM being delivered

Question 13: A flow hood is placed over a return grille instead of a supply register. What can it measure there?

The CFM of air being pulled back into the return duct at that location
The static pressure of the outdoor condenser
The refrigerant superheat
The gas valve pressure

Question 14: Which situation would most likely cause overall system CFM to drop even though the blower motor itself is working normally?

The thermostat display is dim
A dirty air filter increasing resistance in the airflow path
The outdoor temperature is mild
The homeowner recently vacuumed the house

Question 15: A system is designed to deliver 1,200 CFM total. Flow hood readings at all registers add up to only 900 CFM. What does this most likely indicate?

The system is performing better than designed
The flow hood readings should be ignored
The system is not delivering its designed airflow, possibly due to duct leakage, restrictions, or blower issues
This is normal and requires no further checks

Question 16: Which measurement would be most useful for confirming a specific bedroom is receiving enough conditioned air?

Total external static pressure at the equipment
Outdoor ambient temperature
Refrigerant subcooling at the outdoor unit
CFM measured at that room's supply register with a flow hood

Question 17: Which of the following is NOT something an anemometer is normally used for?

Measuring refrigerant pressure in the suction line
Checking air velocity at a supply register
Checking air velocity at a return grille
Estimating airflow when combined with an opening's free area

Question 18: True or False: A system can have acceptable static pressure at the equipment and still deliver poor CFM to individual rooms.

False, static pressure at the equipment guarantees good airflow everywhere
True
False, this situation cannot occur in a properly wired system
True, but only in heating mode

Question 19: A technician replaces a clogged filter and airflow improves noticeably. What does this confirm about the relationship between the filter and CFM?

Filters have no real effect on airflow
The refrigerant charge was adjusted by replacing the filter
The dirty filter had been restricting airflow, and reducing that resistance allowed CFM to increase
The blower motor was replaced by changing the filter

Question 20: Which best describes the relationship between static pressure and CFM for a fixed blower speed?

They have no relationship at all
As static pressure increases, CFM also always increases
CFM stays exactly fixed no matter how much static pressure changes
As static pressure (resistance) increases, CFM generally decreases

Question 21: A technician is comparing airflow between two rooms. Room 1 reads 120 CFM and Room 2 reads 60 CFM at the supply register, but both rooms were designed for 100 CFM. What is the likely conclusion?

Room 1 is receiving more air than needed, while Room 2 is under-delivering, suggesting a balancing issue
Both rooms are performing exactly as designed
The flow hood must be defective since the readings differ
This is normal and no adjustment is ever needed

Question 22: A technician wants to check whether a return duct is undersized. Which measurement would help most?

Refrigerant subcooling at the outdoor unit
CFM or velocity at the return grille, compared to what the system needs to pull back to the equipment
The color of the return grille
The gas manifold pressure

Question 23: True or False: An undersized return duct can restrict system airflow just as much as a supply-side restriction.

False, only supply-side restrictions matter
False, the return side has no effect on system airflow
True
True, but only during heating mode

Question 24: A technician measures airflow before and after cleaning a dirty evaporator coil. What result would confirm the coil was restricting airflow?

CFM decreases after the coil is cleaned
CFM stays exactly the same regardless of coil condition
Static pressure increases after the coil is cleaned
CFM increases after the coil is cleaned

Question 25: Which of these best describes a practical use of airflow measurement in the field?

Confirming a system is delivering the CFM it was designed to deliver
Determining the exact refrigerant charge needed
Setting the thermostat's heating and cooling schedule
Calculating the homeowner's utility bill

Question 26: A duct system has several sharp 90-degree turns. What effect would this most likely have on CFM, compared to a system with smoother transitions?

Higher CFM, because sharp turns speed up the air
Lower CFM, because sharp turns add resistance to the airflow path
No effect on CFM at all
CFM cannot be affected by duct fittings

Question 27: A technician records CFM readings at every register and adds them together to estimate total system airflow. What is a limitation of this method compared to measuring at the equipment?

This method is always more accurate than any other method
Register readings can never be added together for any purpose
Small measurement errors at each register can add up, so the total may differ somewhat from a reading taken directly at the equipment
This method measures refrigerant charge instead of airflow

Question 28: Which statement is TRUE about CFM and comfort?

CFM has no connection to room comfort
More CFM to a room is always better, with no downside
CFM only matters in commercial buildings
Delivering the correct design CFM to each room supports proper heating and cooling comfort in that room

Question 29: A technician suspects a duct leak between the equipment and a register because the register's measured CFM is much lower than the total system CFM would suggest. What should be checked?

The duct run between the equipment and that register, for gaps, disconnected joints, or unsealed seams
The thermostat batteries
The outdoor unit's refrigerant charge
The gas valve at the furnace

Question 30: Overall, why does a technician measure both static pressure and CFM rather than just one of them?

Only static pressure matters; CFM is not useful in the field
Each measurement reveals different information, so using both gives a fuller picture of system airflow performance
Only CFM matters; static pressure is not useful in the field
They always give identical readings, so checking both is redundant

EXAM CARD NATE_AIRDIST_SERVICE

Questions30

Time limit30 min

Pass score70%

Code editionNEC 2023

DifficultyIntermediate

Last reviewedJun 2026

Timer starts immediately. Progress is auto-saved.

Source: NEC 2026 (NFPA 70)