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NATE_AIRDIST_SERVICE NEC 2023

NATE Air Distribution Service Practice Test 9

This test covers filters and MERV ratings: what MERV measures, the trade-off between filtration and airflow resistance, and how filter condition affects static pressure and CFM over time.

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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: A higher MERV rating captures smaller particles but can add more resistance. The system's blower and duct design need to be matched to the filter chosen.

30

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30 min

Time

70%

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NATE Air Distribution Service Practice Test 9 — Question List

Question 1: What does MERV stand for?

Minimum Efficiency Reporting Value
Maximum Equipment Rated Velocity
Mechanical Energy Recovery Value
Motor Efficiency Rating Verification

Question 2: What does a higher MERV rating generally indicate about a filter?

It always uses less electricity
It captures smaller particles than a lower MERV filter
It never needs to be replaced
It automatically increases the equipment's rated static pressure

Question 3: What is a potential trade-off of choosing a higher MERV filter?

It always reduces the equipment's rated static pressure
It eliminates the need for duct sealing
It can increase resistance to airflow (higher static pressure) if the system was not designed for it
It automatically converts a PSC motor to an ECM motor

Question 4: True or False: A dirty filter increases static pressure regardless of its MERV rating.

False, only low-MERV filters get dirty enough to matter
False, only high-MERV filters increase static pressure
False, filter condition has no effect on static pressure
True

Question 5: A homeowner upgrades from a low-MERV filter to a high-MERV filter without any other system changes. After the upgrade, static pressure rises noticeably above the equipment's rated value. What is the most likely explanation?

The new filter's higher resistance is more than the system's blower and duct design were set up to handle
The refrigerant charge automatically changed
The thermostat needs recalibration
Higher MERV filters always lower static pressure, so this could not happen

Question 6: Which of the following filters would generally be expected to capture the smallest particles?

A MERV 6 filter
A MERV 13 filter
A MERV 4 filter
A MERV 1 filter

Question 7: A technician measures static pressure across a filter (before and after) and finds a larger-than-expected pressure drop, even though the filter looks only lightly dirty. What could explain this?

This is impossible; only dirty filters can cause a pressure drop
The manometer must be broken
The filter's MERV rating may be higher than the system's design intended, adding more resistance than expected even when relatively clean
The refrigerant charge is affecting the reading

Question 8: What should be checked before recommending a much higher MERV filter for a homeowner concerned about air quality?

The color of the filter frame
The homeowner's thermostat brand
The refrigerant type used by the outdoor unit
Whether the system's blower and duct design can handle the added resistance without pushing static pressure above the rated value

Question 9: Why does a filter's resistance to airflow generally increase over time, even without a MERV rating change?

As the filter collects dust and debris, the openings for air to pass through become smaller and more restricted
The filter's MERV rating decreases automatically over time
The refrigerant charge slowly leaks into the filter
The filter material physically shrinks with age

Question 10: A technician replaces a dirty MERV 8 filter with a new MERV 8 filter of the same size and thickness. What is the expected effect on static pressure right after the change?

Static pressure should rise significantly
Static pressure should drop, since the new filter has much less accumulated resistance than the dirty one
Static pressure should stay exactly the same
Static pressure cannot be affected by filter changes

Question 11: True or False: All filters with the same MERV rating will have identical airflow resistance, regardless of thickness or design.

True, MERV rating alone fully determines resistance
True, thickness and design never affect resistance
False
False, but only for filters below MERV 8

Question 12: A homeowner wants better filtration for allergy concerns but has an older system with a PSC blower motor and no history of handling high-resistance filters. What is a reasonable recommendation?

Immediately install the highest MERV filter available with no further checks
Tell the homeowner filtration cannot be improved on any older system
Remove the filter entirely to maximize airflow
Consider a moderate MERV upgrade and check static pressure after installation, rather than jumping to the highest MERV rating available

Question 13: What is a simple, common maintenance recommendation related to filters that helps prevent airflow problems?

Replacing or cleaning the filter on a regular schedule, rather than waiting until airflow is noticeably reduced
Only replacing the filter once every five years
Removing the filter entirely to reduce resistance
Sealing the filter rack shut permanently

Question 14: A technician measures static pressure across a clean, correctly matched filter and finds only a small pressure drop. What does this indicate?

The filter must be installed backward
The filter is not adding significant resistance in its current, clean state, which is expected for a properly matched filter
The manometer is malfunctioning
The filter has no MERV rating at all

Question 15: A system's rated static pressure is 0.50 in. w.c. With a new MERV 8 filter installed, TESP measures 0.45 in. w.c. After three months without replacement, TESP measures 0.68 in. w.c. What is the most likely cause of the increase?

The filter's MERV rating automatically increased over time
The equipment's rated static pressure changed
The filter has accumulated dirt over the three months, adding resistance to airflow
The refrigerant charge caused the increase

Question 16: Which statement correctly describes the general relationship between MERV rating and airflow resistance, all else being equal?

Higher MERV ratings always mean exactly the same resistance as lower MERV ratings
MERV rating has no relationship to airflow resistance whatsoever
Lower MERV ratings always have higher resistance than higher MERV ratings
Higher MERV ratings can mean higher airflow resistance, though filter design and thickness also play a role

Question 17: A technician notices a homeowner has installed a filter that does not fit properly in the filter rack, leaving gaps around the edges. What problem does this cause?

Unfiltered air can bypass the filter through the gaps, reducing the effectiveness of filtration
This always increases the filter's MERV rating
This has no effect since the filter still fits in the rack
This automatically raises static pressure to unsafe levels

Question 18: True or False: Choosing a filter with a MERV rating matched to the system's design is important for balancing filtration and airflow.

False, MERV rating never needs to match the system design
True
False, only filter size matters, never MERV rating
True, but only for commercial systems

Question 19: A system with an ECM blower motor is fitted with a higher MERV filter than before. What is a likely difference in symptoms compared to the same change on a PSC system?

There would be no difference between the two systems
The PSC system would show less obvious airflow reduction than the ECM system
The ECM system may show less obvious airflow reduction at first, since the motor compensates by increasing speed, while the PSC system's CFM would drop more noticeably
Neither system type can be affected by a MERV rating change

Question 20: Which of these best describes what MERV rating measures?

A filter's exact static pressure drop at all times
A filter's refrigerant compatibility
A filter's physical size in inches
A filter's ability to capture particles of different sizes, on a standardized scale

Question 21: A technician is asked to explain to a homeowner why "the highest MERV rating available" is not always the best choice. What is the best explanation?

Because a very high MERV filter can add more resistance than the system's blower and ducts were designed to handle, potentially reducing airflow and system performance
Because higher MERV filters are illegal in residential systems
Because higher MERV filters always cost the same as lower MERV filters
Because MERV rating has no effect on filtration quality at all

Question 22: True or False: A dirty low-MERV filter can, in some cases, cause more resistance than a clean high-MERV filter.

False, MERV rating alone always determines which filter has more resistance
True
False, dirty filters never add meaningful resistance
True, but only for filters rated MERV 13 or higher

Question 23: A technician is called because a system's airflow dropped noticeably right after a filter change. What is a reasonable first thing to verify?

Whether the thermostat schedule was changed recently
Whether the homeowner painted a room recently
Whether the new filter has a significantly different (higher) MERV rating or thickness than the one it replaced
Whether the refrigerant charge was adjusted

Question 24: Which statement about MERV ratings and static pressure testing is TRUE?

Static pressure testing cannot be used to evaluate filters
MERV rating alone eliminates the need for static pressure testing
Only refrigerant gauges can be used to evaluate a filter's resistance
Comparing static pressure across a filter before and after replacement helps confirm whether the filter was a significant source of restriction

Question 25: What is a reasonable approach when a homeowner wants improved filtration but the system has a history of high static pressure readings?

Address the existing static pressure issues first, and consider filtration options that do not add significant additional resistance
Install the highest MERV filter available regardless of the existing static pressure problem
Tell the homeowner filtration and static pressure are unrelated topics
Remove the filter entirely to solve both problems at once

Question 26: A pleated filter and a flat fiberglass panel filter share the same MERV rating. Which is generally expected to offer more surface area for airflow to pass through?

The flat fiberglass panel filter, since it is thinner
The pleated filter, due to its folded design increasing surface area
Neither filter has any surface area relevant to airflow
Surface area is not a real factor in filter design

Question 27: True or False: Checking static pressure only immediately after a filter change, and never again, is a good long-term maintenance strategy.

True, one check is always sufficient for the life of the filter
True, static pressure never changes after the initial reading
False
False, but only for filters rated below MERV 8

Question 28: Which best summarizes the practical lesson of the filtration versus airflow resistance trade-off?

Filtration quality should always be the only consideration, regardless of airflow
Airflow should always be the only consideration, regardless of filtration
MERV rating and airflow resistance are completely unrelated topics
Better filtration (higher MERV) is valuable, but it must be balanced against the system's ability to handle the added resistance to airflow

Question 29: A technician is asked to help a homeowner choose between a MERV 8 and a MERV 11 filter for their existing system. What information would be most helpful in making this recommendation?

The system's rated static pressure, current TESP readings, and whether the design can accommodate the added resistance of the higher MERV option
The homeowner's favorite color
The refrigerant type used by the outdoor unit
The brand of thermostat installed

Question 30: Overall, why is filter knowledge, including MERV ratings, an important part of NATE Air Distribution Service competency?

Filters have no real connection to airflow performance
Filters are one of the most common and easily checked sources of airflow restriction, and understanding MERV helps technicians make informed recommendations
MERV ratings are only relevant to commercial buildings
Filter knowledge is not tested on the real NATE exam

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)