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Free CIH Practice Questions

10 free, exam-style Certified Industrial Hygienist (CIH) practice questions with answers and explanations. No signup required. Work through them below, then take the full free CIH practice test to study every exam domain.

These 10 free CIH questions are organized by exam domain, so you can see how each part of the Certified Industrial Hygienist blueprint is tested. Reveal the answer and explanation under each question.

Domain 1: Exposure Assessment Principles and Practice

Question 1

An industrial hygienist needs to assess worker exposure during a specific high-exposure task lasting 45 minutes. Which sampling strategy is MOST appropriate?

  1. Full-shift personal sampling
  2. Task-based personal sampling
  3. Area sampling near the process
  4. Grab sampling at random intervals
Show answer & explanation

Correct answer: B - Task-based personal sampling

Question 2

The D50 cut point for the respirable fraction according to ACGIH/ISO criteria is:

  1. 2.5 μm
  2. 4.0 μm
  3. 10 μm
  4. 100 μm
Show answer & explanation

Correct answer: B - 4.0 μm

Question 3

The PCM method counts fibers that are:

  1. All sizes visible under the microscope
  2. Greater than 5 μm length, less than 3 μm width, with aspect ratio greater than 3:1
  3. Only asbestos fibers specifically identified
  4. Greater than 10 μm in length
Show answer & explanation

Correct answer: B - Greater than 5 μm length, less than 3 μm width, with aspect ratio greater than 3:1

Question 4

To convert a concentration from ppm to mg/m³ at 25°C and 1 atm, the formula is:

  1. mg/m³ = ppm × 24.45 / MW
  2. mg/m³ = ppm × MW / 24.45
  3. mg/m³ = ppm / MW
  4. mg/m³ = ppm × MW
Show answer & explanation

Correct answer: B - mg/m³ = ppm × MW / 24.45

Question 5

For mixtures of chemicals with similar toxic effects, the combined exposure is typically assessed using:

  1. The highest single concentration
  2. Additive mixture formula (sum of C/TLV ratios)
  3. The lowest TLV in the mixture
  4. Multiplication of concentrations
Show answer & explanation

Correct answer: B - Additive mixture formula (sum of C/TLV ratios)

Question 6

Carbon monoxide exerts its toxic effect primarily by:

  1. Irritating the respiratory tract
  2. Binding to hemoglobin with high affinity, forming carboxyhemoglobin
  3. Causing liver damage
  4. Sensitizing the immune system
Show answer & explanation

Correct answer: B - Binding to hemoglobin with high affinity, forming carboxyhemoglobin

Domain 2: Control Selection, Recommendation/Implementation, and Validation

Question 7

If fan speed is doubled, the power requirement will increase by a factor of:

  1. 2
  2. 4
  3. 8
  4. 16
Show answer & explanation

Correct answer: C - 8

Question 8

When two sound sources of equal level are combined, the total level increases by approximately:

  1. 0 dB
  2. 3 dB
  3. 6 dB
  4. 10 dB
Show answer & explanation

Correct answer: B - 3 dB

Question 9

The three principles of radiation protection are:

  1. Detection, measurement, and reporting
  2. Time, distance, and shielding
  3. Source, pathway, and receptor
  4. Primary, secondary, and tertiary prevention
Show answer & explanation

Correct answer: B - Time, distance, and shielding

Question 10

For outdoor work with a solar load, the WBGT is calculated as:

  1. WBGT = 0.7 WB + 0.3 GT
  2. WBGT = 0.7 WB + 0.2 GT + 0.1 DB
  3. WBGT = WB + GT + DB
  4. WBGT = DB only
Show answer & explanation

Correct answer: B - WBGT = 0.7 WB + 0.2 GT + 0.1 DB

The rest of the CIH blueprint

The CIH exam also covers these domains. Drill them in the full free practice test:

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