CHT Equipment Operation & Maintenance 2 — Questions and Answers
Question 1: Which type of valve is most commonly used as a primary shut-off on hyperbaric chamber oxygen supply lines due to its clean-service compatibility?
- Ball valve (Correct answer)
- Gate valve
- Butterfly valve
- Needle valve
Correct answer: Ball valve
Ball valves are preferred on oxygen lines because they open fully with a quarter-turn, leave no dead space, and are available in oxygen-clean configurations.
Question 2: What is the minimum recommended frequency for changing the desiccant in a hyperbaric chamber's air drying system under normal operational use?
- Per manufacturer schedule or when saturation indicator changes (Correct answer)
- Every 24 hours regardless of use
- Monthly regardless of humidity readings
- Only when the chamber dewpoint exceeds 50°F
Correct answer: Per manufacturer schedule or when saturation indicator changes
Desiccant replacement frequency is driven by the manufacturer's schedule and color-indicator saturation, not a fixed calendar interval.
Question 3: A hyperbaric technician notices the chamber's built-in breathing system (BIBS) mask check valve is leaking gas into the chamber environment. The IMMEDIATE corrective action is to:
- Remove the mask from service and replace the check valve before next use (Correct answer)
- Continue operation and monitor CO2 levels closely
- Increase chamber ventilation rate to compensate
- Switch the patient to free-flow O2 and continue the treatment
Correct answer: Remove the mask from service and replace the check valve before next use
A leaking BIBS check valve enriches the chamber oxygen concentration and creates a fire hazard, so the mask must be removed from service immediately.
Question 4: What is the purpose of a pressure-relief valve (PRV) on a hyperbaric chamber hull?
- To prevent the chamber from exceeding its maximum allowable working pressure (Correct answer)
- To vent oxygen during a fire emergency
- To equalize pressure between inner and outer lock
- To regulate therapeutic oxygen flow to the patient
Correct answer: To prevent the chamber from exceeding its maximum allowable working pressure
The PRV is a safety device that automatically vents gas if chamber pressure exceeds the MAWP, protecting structural integrity.
Question 5: When lubricating O-ring seals on a hyperbaric chamber door, which lubricant is acceptable for use?
- Oxygen-compatible, silicone-based lubricant approved for the seal material (Correct answer)
- Petroleum-based grease such as WD-40
- Any food-grade oil
- Dry graphite powder only
Correct answer: Oxygen-compatible, silicone-based lubricant approved for the seal material
Only oxygen-compatible, material-compatible lubricants (typically silicone-based) may be used to prevent seal degradation and fire risk.
Question 6: During multiplace chamber operations, the intercommunication system fails mid-treatment. Per NFPA 99 and UHMS guidelines, the operator should:
- Establish an alternative communication method before continuing and follow facility emergency protocols (Correct answer)
- Terminate the treatment immediately by performing an emergency ascent
- Continue treatment using predetermined hand signals only
- Increase monitoring frequency and continue without interruption
Correct answer: Establish an alternative communication method before continuing and follow facility emergency protocols
Facilities must have backup communication plans; an alternative means must be established and verified before continuing patient treatment.
Question 7: The purpose of a hyperbaric chamber's ventilation system during an oxygen treatment is primarily to:
- Maintain chamber oxygen concentration below flammable levels by purging with air (Correct answer)
- Deliver supplemental oxygen directly to the patient
- Cool the chamber interior temperature
- Reduce carbon dioxide buildup from the chamber compressor
Correct answer: Maintain chamber oxygen concentration below flammable levels by purging with air
Ventilation dilutes and exhausts oxygen that leaks from BIBS masks, keeping the ambient O2 level below the fire-risk threshold (typically ≤23.5%).
CHT Equipment Operation & Maintenance 2
Which type of valve is most commonly used as a primary shut-off on hyperbaric chamber oxygen supply lines due to its clean-service compatibility?