CPFT Pulmonary Function Technologist Certification Exam 2026:
Comprehensive NBRC Practice Test — Pulmonary Function Testing,
Lung Volumes, Spirometry, Gas Exchange, Quality Assurance &
Clinical Interpretation — 190 Multiple-Choice Questions with
Answers & Detailed Rationales
Domain I: Instrumentation / Equipment (63 Questions)
Question 1
A technologist is preparing a spirometer for daily calibration. According to ATS/ERS
standards, which of the following is the minimum acceptable accuracy for a calibration
syringe?
A. ±1% of the syringe volume
B. ±2% of the syringe volume
C. ±3% of the syringe volume
D. ±5% of the syringe volume
Correct Answer: C
Explanation: ATS/ERS standards require calibration syringes to have an accuracy of ±3% or
±0.5% depending on the specification referenced. The 3-L syringe should be accurate within
±3% of its stated volume to ensure valid spirometry calibration.
Question 2
During a body plethysmography quality control check, the technologist notes that the box
pressure transducer is drifting. What is the most appropriate initial action?
A. Replace the pressure transducer immediately
B. Perform a biological control test
,C. Check for leaks in the breathing valve and mouthpiece
D. Recalibrate the plethysmograph according to manufacturer specifications
Correct Answer: D
Explanation: Pressure transducer drift is typically corrected by recalibration. Replacement is
premature until recalibration fails. Biological controls assess overall system performance, not
transducer calibration specifically.
Question 3
A technologist is setting up a DLCO system. What is the required 0–90% response time for
the carbon monoxide analyzer according to ATS/ERS 2017 standards?
A. ≤50 ms
B. ≤100 ms
C. ≤150 ms
D. ≤200 ms
Correct Answer: C
Explanation: The ATS/ERS 2017 DLCO standards specify that the 0–90% response time for
the CO analyzer must be ≤150 ms. Faster response times reduce error in DLCO measurement
due to signal alignment issues.
Question 4
Which of the following best describes the purpose of a biological control in a pulmonary
function laboratory?
A. To calibrate the spirometer daily
,B. To verify that the equipment produces values within a predetermined range for a healthy
individual
C. To test the electrical safety of all equipment
D. To measure the technologist's own lung function for research purposes
Correct Answer: B
Explanation: Biological controls use a healthy, stable individual to verify that the entire
testing system is functioning properly and producing expected results. It detects system
errors that calibration alone may miss.
Question 5
A technologist notices that the spirometer's volume readings are consistently 5% higher than
the calibration syringe volume. What is the most likely cause?
A. The patient is not sealing their lips properly around the mouthpiece
B. The spirometer is not properly calibrated
C. The calibration syringe is too warm
D. The flow sensor is obstructed
Correct Answer: B
Explanation: Consistent over-reading on calibration indicates a calibration error. Patient
technique issues would not affect syringe calibration. Temperature affects gas volume but
would not cause a consistent 5% over-read.
Question 6
What is the recommended frequency for leak testing a volume-displacement spirometer?
A. Before each patient test
, B. Daily
C. Weekly
D. Monthly
Correct Answer: B
Explanation: ATS/ERS standards recommend daily leak testing for volume-type spirometers.
Leaks in the system can cause underestimation of volumes and invalid test results.
Question 7
A technologist is calibrating a plethysmograph. Which of the following is used to verify the
accuracy of the box pressure signal?
A. A 3-L calibration syringe
B. A known volume of gas injected into the box with the patient absent
C. A biological control subject
D. A pressure manometer connected to the mouthpiece
Correct Answer: B
Explanation: Box pressure calibration is verified by injecting a known volume (typically 30–50
mL) into the closed box and checking the pressure response. This assesses the relationship
between pressure changes and volume.
Question 8
Which of the following equipment malfunctions would most likely result in falsely elevated
DLCO values?
A. A leak in the mouthpiece
Comprehensive NBRC Practice Test — Pulmonary Function Testing,
Lung Volumes, Spirometry, Gas Exchange, Quality Assurance &
Clinical Interpretation — 190 Multiple-Choice Questions with
Answers & Detailed Rationales
Domain I: Instrumentation / Equipment (63 Questions)
Question 1
A technologist is preparing a spirometer for daily calibration. According to ATS/ERS
standards, which of the following is the minimum acceptable accuracy for a calibration
syringe?
A. ±1% of the syringe volume
B. ±2% of the syringe volume
C. ±3% of the syringe volume
D. ±5% of the syringe volume
Correct Answer: C
Explanation: ATS/ERS standards require calibration syringes to have an accuracy of ±3% or
±0.5% depending on the specification referenced. The 3-L syringe should be accurate within
±3% of its stated volume to ensure valid spirometry calibration.
Question 2
During a body plethysmography quality control check, the technologist notes that the box
pressure transducer is drifting. What is the most appropriate initial action?
A. Replace the pressure transducer immediately
B. Perform a biological control test
,C. Check for leaks in the breathing valve and mouthpiece
D. Recalibrate the plethysmograph according to manufacturer specifications
Correct Answer: D
Explanation: Pressure transducer drift is typically corrected by recalibration. Replacement is
premature until recalibration fails. Biological controls assess overall system performance, not
transducer calibration specifically.
Question 3
A technologist is setting up a DLCO system. What is the required 0–90% response time for
the carbon monoxide analyzer according to ATS/ERS 2017 standards?
A. ≤50 ms
B. ≤100 ms
C. ≤150 ms
D. ≤200 ms
Correct Answer: C
Explanation: The ATS/ERS 2017 DLCO standards specify that the 0–90% response time for
the CO analyzer must be ≤150 ms. Faster response times reduce error in DLCO measurement
due to signal alignment issues.
Question 4
Which of the following best describes the purpose of a biological control in a pulmonary
function laboratory?
A. To calibrate the spirometer daily
,B. To verify that the equipment produces values within a predetermined range for a healthy
individual
C. To test the electrical safety of all equipment
D. To measure the technologist's own lung function for research purposes
Correct Answer: B
Explanation: Biological controls use a healthy, stable individual to verify that the entire
testing system is functioning properly and producing expected results. It detects system
errors that calibration alone may miss.
Question 5
A technologist notices that the spirometer's volume readings are consistently 5% higher than
the calibration syringe volume. What is the most likely cause?
A. The patient is not sealing their lips properly around the mouthpiece
B. The spirometer is not properly calibrated
C. The calibration syringe is too warm
D. The flow sensor is obstructed
Correct Answer: B
Explanation: Consistent over-reading on calibration indicates a calibration error. Patient
technique issues would not affect syringe calibration. Temperature affects gas volume but
would not cause a consistent 5% over-read.
Question 6
What is the recommended frequency for leak testing a volume-displacement spirometer?
A. Before each patient test
, B. Daily
C. Weekly
D. Monthly
Correct Answer: B
Explanation: ATS/ERS standards recommend daily leak testing for volume-type spirometers.
Leaks in the system can cause underestimation of volumes and invalid test results.
Question 7
A technologist is calibrating a plethysmograph. Which of the following is used to verify the
accuracy of the box pressure signal?
A. A 3-L calibration syringe
B. A known volume of gas injected into the box with the patient absent
C. A biological control subject
D. A pressure manometer connected to the mouthpiece
Correct Answer: B
Explanation: Box pressure calibration is verified by injecting a known volume (typically 30–50
mL) into the closed box and checking the pressure response. This assesses the relationship
between pressure changes and volume.
Question 8
Which of the following equipment malfunctions would most likely result in falsely elevated
DLCO values?
A. A leak in the mouthpiece
