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100+ Free CIE Practice Questions

Pass your ACAC Council-certified Indoor Environmentalist (CIE) exam on the first try — instant access, no signup required.

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Which is the BEST general approach when a CIE finds an issue OUTSIDE their expertise (e.g., advanced HVAC engineering, structural)?

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2026 Statistics

Key Facts: CIE Exam

100

Exam Questions

ACAC Candidate Handbook

75%

Passing Score

ACAC Candidate Handbook

3 hours

Exam Duration (closed-book)

ACAC Candidate Handbook

$500

Total Fee ($400 cert + $100 exam)

ACAC fees page

2 years

Field Experience Required (1 yr with degree)

ACAC

4 pCi/L

EPA Radon Action Level

EPA

40 RCs

Recertification Credits per 2-year Cycle

ACAC

The ACAC CIE (Council-certified Indoor Environmentalist) is the professional certification for indoor air quality (IAQ) practitioners issued by the American Council for Accredited Certification (ACAC). It is broader than mold-focused credentials and covers VOCs, formaldehyde, radon, particulate matter, CO/CO2, asbestos, lead, mold, and HVAC assessment. The 100-question, 3-hour, closed-book exam (75% passing score) covers indoor air pollutants, ASHRAE 62.1 ventilation, ASHRAE 55 thermal comfort, sampling and monitoring, AHERA/RRP regulations, LEED v4 IEQ, and the ACAC Code of Ethics. Prerequisites: 2 years field experience in IAQ (1 year with a qualifying degree). Certification is valid for 2 years and requires 40 Recertification Credits for renewal.

Sample CIE Practice Questions

Try these sample questions to test your CIE exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1Which ASHRAE standard establishes minimum ventilation rates for acceptable indoor air quality in commercial and institutional buildings?
A.ASHRAE 90.1
B.ASHRAE 62.1
C.ASHRAE 55
D.ASHRAE 189.1
Explanation: ASHRAE 62.1 (Ventilation for Acceptable Indoor Air Quality) specifies minimum outdoor air ventilation rates and other measures to provide acceptable IAQ. It uses a Ventilation Rate Procedure with per-person and per-area components.
2ASHRAE 55 addresses which environmental quality factor?
A.Outdoor air ventilation rates
B.Thermal comfort conditions for human occupancy
C.Energy efficiency
D.Acoustic performance
Explanation: ASHRAE 55 establishes conditions (temperature, humidity, air velocity, mean radiant temperature, clothing, activity) that provide thermal comfort for at least 80% of building occupants, using the PMV/PPD model.
3OSHA's PEL for formaldehyde is:
A.0.1 ppm 8-hr TWA
B.0.75 ppm 8-hr TWA with action level 0.5 ppm
C.5 ppm STEL only
D.No PEL
Explanation: OSHA's formaldehyde standard (29 CFR 1910.1048) sets an 8-hour PEL of 0.75 ppm and an action level of 0.5 ppm, with a 2 ppm short-term (15-min) exposure limit. ATSDR's chronic Minimal Risk Level is much lower (~8 ppb).
4EPA's action level for residential radon is:
A.0.4 pCi/L
B.2 pCi/L
C.4 pCi/L
D.20 pCi/L
Explanation: EPA's recommended action level is 4 pCi/L. Mitigation is encouraged at 2-4 pCi/L. WHO recommends a lower 2.7 pCi/L action level. CIEs must know the U.S. number.
5OSHA's PEL for carbon monoxide is:
A.5 ppm 8-hr TWA
B.50 ppm 8-hr TWA
C.100 ppm STEL only
D.1,000 ppm
Explanation: OSHA's CO PEL is 50 ppm as an 8-hour TWA. NIOSH REL is 35 ppm and ACGIH TLV is 25 ppm. Most IAQ-focused criteria are lower than the OSHA PEL.
6Which CO2 concentration is often used as a rule-of-thumb proxy for adequate ventilation in occupied spaces?
A.200 ppm
B.600 ppm
C.1,000 ppm (or 700 ppm above outdoor)
D.5,000 ppm
Explanation: A common rule-of-thumb threshold is approximately 1,000 ppm (or ~700 ppm above outdoor) as an indicator of sufficient ventilation in occupied spaces. CO2 itself is not a health hazard at typical indoor levels — it is a proxy.
7Which MERV rating is the typical minimum that ASHRAE 62.1 has historically recommended for general air-handling system filtration?
A.MERV 1
B.MERV 4
C.MERV 8
D.HEPA
Explanation: ASHRAE 62.1 has historically required MERV 8 minimum particle filtration in air-handling units. Recent ASHRAE guidance and LEED v4 push higher (MERV 13+) for better fine-particle and bioaerosol capture.
8HEPA filters are defined as removing at least what efficiency of particles at 0.3 µm?
A.85%
B.95%
C.99.97%
D.100%
Explanation: HEPA filters are defined as 99.97% efficient at the most-penetrating particle size (typically 0.3 µm). ULPA filters are 99.999% efficient. Mold spores, asbestos fibers, and many fine particulates fall within the capture range.
9Which regulation governs asbestos in U.S. schools and is administered by EPA?
A.OSHA 1910.1001
B.AHERA (40 CFR Part 763)
C.NESHAP
D.RRP rule
Explanation: AHERA (40 CFR Part 763) is EPA's Asbestos Hazard Emergency Response Act rule for schools. It requires inspections, management plans, and licensed inspectors/abatement. OSHA 1910.1001 covers occupational exposure; NESHAP covers renovation/demolition emissions.
10Which EPA rule requires lead-safe work practices in pre-1978 housing and child-occupied facilities during renovation?
A.AHERA
B.RRP rule (40 CFR Part 745, Subpart E)
C.NESHAP
D.TSCA Section 4
Explanation: EPA's RRP (Renovation, Repair, and Painting) rule under 40 CFR Part 745 Subpart E requires certified renovators and lead-safe work practices when disturbing more than 6 sq ft (interior) or 20 sq ft (exterior) of paint in pre-1978 housing and child-occupied facilities.

About the CIE Exam

The CIE credential certifies competency in indoor environmental assessment including pollutant identification, HVAC evaluation, ASHRAE 62.1 ventilation standards, sampling/monitoring, and professional reporting across residential and commercial buildings.

Questions

100 scored questions

Time Limit

3 hours

Passing Score

75%

Exam Fee

$500 (certification + exam) (ACAC (American Council for Accredited Certification))

CIE Exam Content Outline

~25%

Indoor Air Pollutants

VOCs, formaldehyde, radon, PM2.5/PM10, CO/CO2, asbestos, lead, mold, bioaerosols

~20%

HVAC & Building Science

ASHRAE 62.1, ASHRAE 55, MERV/HEPA filtration, air change rates, BAS, moisture management

~20%

Sampling, Monitoring & Investigation

Direct-reading instruments, passive/active sampling, NIOSH/OSHA methods, calibration, walk-through

~20%

Standards, Codes & Regulations

ASHRAE, EPA IAQ, OSHA, AHERA, RRP, LEED v4 IEQ, WELL

~15%

Health Effects, Reporting & Ethics

SBS/BRI, sensitive populations, recommendation hierarchy, report writing, ACAC Code of Ethics

How to Pass the CIE Exam

What You Need to Know

  • Passing score: 75%
  • Exam length: 100 questions
  • Time limit: 3 hours
  • Exam fee: $500 (certification + exam)

Keys to Passing

  • Complete 500+ practice questions
  • Score 80%+ consistently before scheduling
  • Focus on highest-weighted sections
  • Use our AI tutor for tough concepts

CIE Study Tips from Top Performers

1Master ASHRAE 62.1 ventilation rates — the people component (cfm/person) plus the area component (cfm/sq ft), and how zone-level vs. system-level requirements interact
2Know key exposure limits: OSHA formaldehyde PEL 0.75 ppm (action 0.5 ppm), CO PEL 50 ppm, EPA radon action 4 pCi/L, CO2 ASHRAE 1,000 ppm rule of thumb (proxy for ventilation, not a health limit)
3Understand the recommendation hierarchy: source control > ventilation > filtration > administrative controls > PPE
4Memorize MERV ratings: MERV 8 minimum for general residential, MERV 13+ for finer particulates, HEPA for clean spaces or remediation
5Study ASHRAE 55 thermal comfort — PMV/PPD model, 80% acceptability target, temperature/humidity ranges for summer and winter clothing
6Know AHERA (40 CFR Part 763) for asbestos in schools, NESHAP for renovation/demolition, and RRP (40 CFR Part 745) for lead in pre-1978 housing

Frequently Asked Questions

What is the CIE exam?

The CIE (Council-certified Indoor Environmentalist) exam is administered by ACAC (American Council for Accredited Certification). It tests competency in indoor air quality assessment including pollutant identification (VOCs, formaldehyde, radon, PM, CO/CO2, asbestos, lead), HVAC evaluation, ASHRAE 62.1 ventilation, sampling and monitoring, and professional ethics.

How many questions are on the CIE exam?

The ACAC CIE exam contains 100 multiple-choice questions delivered as a 3-hour, closed-book examination through Kryterion testing centers, with a remote-proctored webcam option also available. A score of 75% is required to pass.

What is the passing score for the CIE exam?

ACAC requires a score of 75% to pass the CIE exam. Scores are graded electronically at the testing facility and are available to candidates immediately upon completion.

What are the prerequisites for the CIE credential?

ACAC requires a high school diploma or GED plus 2 years of documented field experience in indoor air quality. The experience requirement is reduced to 1 year for candidates holding a college degree in science, engineering, or a related field. Candidates must also agree to the ACAC Code of Ethics.

How is the CIE different from the CIEC?

The CIE (Council-certified Indoor Environmentalist) is the standard practitioner credential requiring 2 years of field experience and a 100-question exam. The CIEC (Council-certified Indoor Environmental Consultant) is the senior consulting tier requiring 8 years of experience (or 4 years with a 4-year degree) and a more rigorous 120-question exam. CIEC holders lead complex investigations and provide expert testimony.

How long is the CIE certification valid?

The CIE certification is valid for 2 years from the date of issue. Holders must accumulate 40 Recertification Credits (RCs) — each representing 1 hour of continuing education or professional development — prior to expiration to maintain the credential.

How long should I study for the CIE exam?

Most candidates prepare for 80-120 hours over 6-10 weeks. Prioritize ASHRAE 62.1 ventilation requirements, formaldehyde and VOC exposure limits, radon (EPA action level 4 pCi/L), particulate matter, ASHRAE 55 thermal comfort, MERV filtration ratings, AHERA asbestos, and the RRP lead rule.