100+ Free Odor Control Technician Practice Questions

No prior IICRC certification is required for the OCT. Candidates must complete an IICRC-approved Odor Control Technician course (offered both live-stream and in-person by IICRC-approved schools). Students must attend the full course duration to be eligible for the exam — partial attendance disqualifies a candidate from taking the certification exam.

The OCT exam is closed-book, 100 multiple-choice questions, with a 75% passing score. After completing the required OCT course, candidates have a 45-day online testing window in which to take the exam through IICRC's online testing system. The exam fee is $80, which is separate from the cost of the required preparatory course.

The OCT covers three primary odor source categories: (1) Biological — decomposition, pet urine, mold/mildew, sewage, garbage; (2) Combustion — fire and smoke damage (dry smoke from cellulose fires, wet smoke from synthetic fires, protein smoke from cooking-oil fires); and (3) Chemical — fuel-oil spills, VOC off-gassing, industrial solvent contamination. The exam tests both the chemistry of each source category and the appropriate deodorization strategy for each.

Olfactory fatigue (adaptation) is the temporary reduction in perceived odor intensity when an odor is continuously present, due to olfactory receptor neuron adaptation. A technician working in a malodorous environment may stop smelling the odor within minutes — making them unreliable for final verification. The OCT exam tests this concept directly: best practice is to step outside for several minutes (or bring in a fresh observer) before evaluating completion. Single-technician self-verification is the wrong answer on adaptation questions.

Key ozone safety facts: (1) OSHA PEL = 0.1 ppm 8-hour TWA; (2) OSHA STEL = 0.3 ppm 15-minute average; (3) Commercial deodorization ozone exceeds both — areas must be unoccupied during treatment including pets and live plants; (4) Acute effects above PEL include cough, chest tightness, asthma exacerbation, reduced lung function; (5) Ozone has an indoor half-life of about 30 minutes — ventilate and verify with a monitor before re-occupancy; (6) Ozone reacts with indoor VOCs to produce harmful byproducts (formaldehyde, acrolein, ultrafine particles); (7) Ozone damages rubber, natural latex, certain dyes, and oxidizes silver.

Hydroxyl generators use photocatalytic oxidation — UV light + a TiO2 catalyst + ambient water vapor to produce hydroxyl radicals (·OH). Each radical reacts within microseconds, so steady-state oxidant concentration stays comparable to outdoor air (typically under 50 ppb), allowing occupied-space use. Per molecule, hydroxyl is roughly a million times more reactive than ozone. Trade-off: treatment times are days versus hours for ozone shock. Use hydroxyl when occupants must remain or when sensitive materials/people are present; use ozone (with evacuation) when faster shock treatment is appropriate and the space can be cleared.

Pet urine contains uric acid that crystallizes when dry. Uric acid crystals are NOT water-soluble — ordinary detergent cleaning rinses urea and salts but leaves uric acid bonded to substrates. When humidity rises, crystals partially redissolve and release ammonia and amines, causing intermittent odor return. Enzymes (proteases, ureases, uricases) catalytically break down uric acid, urea, and protein residues into water-soluble non-odorous products. They need moisture (apply wet, keep wet for labeled dwell time of 24-72 hours often), appropriate temperature (room temperature optimal — high heat denatures), and should not be mixed with strong oxidizers.