CMI Practice Test

The Certified Mold Inspector (CMI) credential from the American Council for Accredited Certification (ACAC) is for people who inspect buildings for mold and moisture problems. This page gives you free practice sets by topic, worked answers to sample questions, the main exam facts from the ACAC handbook, and a study plan. The exam has 100 questions, a 3-hour limit and a 75% passing score.

CMI Exam at a Glance

What changed for CMI in 2026

• Oct 25, 2026: Number of questions changed to 100 questions, closed-book (previously 100 multiple-choice questions, closed-book).^[1]
• Oct 25, 2026: Score release changed to Immediately after grading (previously Immediately, plus email confirmation).^[2]
• Oct 25, 2026: Retake policy changed to Retest at your convenience by calling ACAC (previously Retest any time after paying the $100 fee).^[2]
• Oct 25, 2026: Registration deadline changed to Up to 90 days from application to complete it (previously Finish the application within 90 days).^[1]
• Oct 25, 2026: Renewal changed to 40 Re-certification Credits every 2 years (previously 40 RCs every 2 years + $400 recertification fee).^[1]
• Oct 25, 2026: Delivery changed to Computer-based, at a testing facility or by online proctoring (previously Computer-based at Kryterion test centers or by online video proctoring; no paper exams).^[2]

What the CMI is and how it works

According to American Council for Accredited Certification, “A score of 75% must be achieved to pass this examination.”^[1]

The CMI exam checks whether a candidate can carry out mold inspection and assessment work to the standard ACAC sets for this certification. It is computer-based and taken in the presence of a proctor, either at a testing facility or through online proctoring.

The exam has 100 questions, is closed-book, and has a 3-hour time limit. ACAC sets the passing mark at 75% using the Modified Angoff method, where the cut score is based on what a minimally qualified candidate should know. Exams are graded electronically, and you see your score right away.

To be eligible you need either a 2-year post-secondary degree (or its equivalent) plus 1 year of microbial sampling experience, or no degree and 2 years of that experience. Once you apply, you have up to 90 days to finish the application process.

If you fail, you can retest whenever you are ready by calling the ACAC office. Each re-examination costs $100. The certification is current for 2 years from the date of issue, and to renew it you need 40 Re-certification Credits every 2 years.

ACAC certification is not the same as a state license. Some states regulate mold inspection separately, and their rules differ, so check with your state as well. Before you apply, confirm the current details in the official CMI handbook at acac.org.

Worked examples: how to reason through CMI questions

These are practice questions written for this site, not questions from the real exam. Each explanation shows why the right answer is right and why the others are wrong.

Example 1

Question: Which type of wall assembly is most prone to interstitial condensation and mold growth in a hot, humid climate?

1. Assembly with a vapor retarder on the interior (warm-in-winter) side, which is the wrong side in a cooling-dominant climate
2. Assembly with exterior rigid foam insulation
3. Assembly with a rainscreen gap between cladding and sheathing
4. Open-joint cladding systems over a weather-resistant barrier

Answer: A. Assembly with a vapor retarder on the interior (warm-in-winter) side, which is the wrong side in a cooling-dominant climate

Explanation:

A is correct. In a hot, humid, cooling-dominant climate, water vapor usually moves from the warm, moist outdoors toward the cool, air-conditioned interior. A vapor retarder on the interior side is the standard cold-climate detail, but here it sits on the cool side of the wall. Moisture moving inward builds up against it or condenses on cool sheathing, and the wall cannot dry to the inside. That is where mold grows.

B is wrong: exterior rigid foam keeps the sheathing warmer and is a common way to lower condensation risk. C is wrong: a rainscreen gap lets water drain and helps the back of the cladding dry. D is wrong: open-joint cladding over a weather-resistant barrier depends on drainage and airflow behind the cladding, which also helps drying.

Rule: put vapor control on the warm, moist side and let the wall dry toward the other side.

Example 2

Question: Which method is used to measure carbon monoxide levels indoors?

1. Infrared thermometer
2. Carbon monoxide detector
3. UV light scanner
4. Humidity gauge

Answer: B. Carbon monoxide detector

Explanation:

B is correct. Carbon monoxide is colorless and odorless, so you can only detect it with a sensor built for that gas, such as a carbon monoxide detector or meter. During an inspection, any fuel-burning appliance is a possible source.

A is wrong: an infrared thermometer measures surface temperature. That helps you find cold spots where condensation may form, but it cannot detect gases. C is wrong: a UV light can show some stains and residues that glow under it, but it does not measure the concentration of anything in the air. D is wrong: a humidity gauge (hygrometer) measures relative humidity. That matters a lot for mold, but it tells you nothing about carbon monoxide.

Rule: pick the instrument by what it actually measures, and do not read one tool's result as evidence about something else.

Example 3

Question: What role does client communication play in mold inspection reporting?

1. It reduces the time spent on the job
2. It helps avoid writing the report
3. It ensures client understanding of the report
4. It is only required for legal reasons

Answer: C. It ensures client understanding of the report

Explanation:

C is correct. A report only helps if the client understands it. Talking the client through it makes sure they see what was found, how serious it is, what was and was not inspected, and what to do next, so they can make an informed decision about remediation.

A is wrong: clear communication often takes more time, not less, and saving time is not the point. B is wrong: talking with the client does not replace the written report, which is the permanent record of the inspection. D is wrong: clear communication does help with liability, for example by setting out the scope and its limits, but that is a side benefit and not the only reason to do it.

Rule: explain findings, limits and recommendations in plain language, and write down what you discussed with the client.

How to use these practice tests

Start by reading the official CMI handbook from ACAC so you know the eligibility rules, the application window and what the exam covers. Then take the Start Practice Test set to get a baseline and see which topics feel weakest.

Spend most of your time on those weak topics. If building science is the gap, work through Moisture Intrusion & Building Science and Building Materials & Construction Systems. For fieldwork, use Mold Identification & Sampling Techniques and Post-Remediation Clearance Testing. For the written side, use Mold Inspection Report Writing.

After each set, read every explanation, including the ones for questions you got right, and write down the general rule in a sentence. Keep these notes short so you can review them the week before the exam.

As test day gets close, practice the way the real exam works: closed-book and timed, aiming for 100 questions in 3 hours. Go back over any topic where you still miss questions, and check your application details with ACAC so nothing is left unfinished.

Sources & last verified

1. American Council for Accredited Certification — number of questions, time limit, passing score, validity (official source). “There are 100 questions on the examination.” Verified Oct 25, 2026 · source checked Oct 23, 2026.
2. American Council for Accredited Certification — retake fee, retake policy, delivery, score release (official source). “Collect the $100 re-examination fee.” Verified Oct 25, 2026 · source checked Oct 23, 2026.

How we verify: editorial & fact-checking policy. Report an error: contact us.