On this page
Asset Type
Manufacturer
Model
Manual Reference
3M Bair Paws Model 875 Warming Unit Service Manual, document/reorder number 202036A, May 2013. Confirm the current manufacturer revision before use.
Manufacturer Recommendation / AEM Status
The manufacturer lists operating-temperature calibration and over-temperature circuit testing every 6 months. Calibration is also required after service procedures. Replace the filter every 6 months or sooner if necessary, clean as needed, and inspect for damage before each use.
Calibration requires the Model 90055 Temperature Test Kit and a calibrated K-type thermocouple thermometer. The steady-state calibration target is 43.0°C +/-0.5°C; do not calibrate above 43°C.
During the over-temperature test, the Over-Temp indicator must illuminate, the audible alarm must sound, the heater must switch off within 2 minutes, and peak test-kit temperature must remain below 56°C. The OT threshold is not adjustable.
After repairs and before return to service, the manufacturer safety inspection includes operating-temperature calibration, OT detection testing, leakage-current testing, and safety-ground continuity testing.
If a facility changes the listed activities or interval, that should be handled under its approved AEM program, risk assessment, maintenance history, and applicable regulatory requirements.
What This PM Procedure Covers
- Identification, condition, mounting, hose, controller, and cord inspection.
- Cleaning and airflow-path inspection.
- Six-month filter replacement.
- Operating-temperature calibration and OT protection testing.
- Electrical safety and post-repair requirements.
- Pass/fail decision and CMMS documentation.
Required Tools and Equipment
- 3M Bair Paws Model 90055 Temperature Test Kit with thermocouple.
- Calibrated thermometer accepting a male subminiature K-type thermocouple connector.
- 2-mm flat-headed screwdriver, small screwdriver, and medium Phillips screwdriver.
- Manufacturer replacement Model 875 filter.
- Damp soft cloth, separate drying cloth, and mild cleaning solution or antimicrobial spray.
- Electrical safety analyzer when required and facility-required PPE.
Step-by-Step PM Procedure
1. Identify and Prepare the Unit
Action: Verify asset and serial numbers, Model 875 identity, voltage rating, location, service history, and current manual revision. Remove the unit from patient use, disconnect the disposable gown, turn the controller off, and unplug it.
Expected outcome: The correct unit is confirmed and safe to inspect.
2. Inspect the Warming Unit
Action: Inspect enclosure, labels, inlet/outlet, hose and couplers, controller and cord, holder, mounting clip, case bottom, fasteners, power cord, plug, ground pin, cord retainer, and equipotential connection for damage, blockage, contamination, fluid intrusion, exposed conductors, or overheating.
Expected outcome: Components are intact, legible, secure, cleanable, and unobstructed.
3. Inspect the Mounting Arrangement
Action: Verify placement on a flat hard surface or secure attachment to the applicable wall, pole, suction-wall, or rail mount. Confirm full seating and secure hardware; a bedrail mount requires its safety strap. For an IV pole, use no higher than 44 inches (112 cm) with a minimum 14-inch (35.6 cm) wheelbase radius.
Expected outcome: The installation is stable and does not block the air intake.
4. Clean the Unit
Action: With power disconnected, wipe the cabinet, controller, and hose exterior with a damp soft cloth and mild solution or antimicrobial spray. Dry separately. Do not immerse components, use a dripping-wet cloth, or use harsh solvents.
Expected outcome: Surfaces are clean, dry, and undamaged.
5. Replace the Filter
Action: Disconnect power. Remove the two dark-purple case-bottom screws, slide the bottom down the hose, replace the filter, then restore the bottom and both screws.
Expected outcome: A clean manufacturer replacement filter is correctly installed and secured.
6. Set Up the Temperature Test
Action: Test in an environment similar to clinical use and within 18-26°C (65-79°F). Connect the hose to the Model 90055 kit, insert the thermocouple through its grommet, center the tip in the test-kit cross section, and extend the hose straight to full length.
Expected outcome: The approved test kit and calibrated thermometer are correctly positioned.
7. Warm the System
Action: Turn the controller fully clockwise to maximum airflow and temperature and warm for 10 minutes. Keep it at maximum during calibration.
Expected outcome: The unit reaches a stable test condition.
8. Calibrate Operating Temperature
Action: Slide the case bottom down the hose to access calibration. Insert the 2-mm screwdriver about one-half inch into the access hole. Turn the potentiometer very slowly until 43°C, then wait at least 5 minutes for steady state.
Expected outcome: Temperature stabilizes at 43.0°C +/-0.5°C. Never calibrate above 43°C.
9. Test the Over-Temperature Circuit
Action: Using a small screwdriver, continuously press the OT test button while monitoring temperature and heater-shutdown time. The test drives the heater full-on and unregulated.
Expected outcome: The OT indicator illuminates, the audible alarm sounds, the heater shuts off within 2 minutes, and peak temperature remains below 56°C.
Failure action: Release the button, turn the controller off, unplug the unit, remove it from service, and contact authorized support. Do not adjust the OT threshold.
10. Reset and Confirm Cool-Down
Action: Turn the controller off, wait 10 seconds, then select the low setting. After several minutes, verify temperature approaches ambient.
Expected outcome: The alarm resets and the unit cools normally without a fault.
11. Reassemble and Function-Test
Action: Restore the case bottom, filter, and both screws without pinching the hose or controller cord. Turn the dial through its range and verify low-setting click-on, increasing airflow and temperature, and absence of abnormal noise, odor, restriction, fault, or shutdown.
Expected outcome: The unit is correctly assembled and operates normally across its range.
12. Perform Electrical Safety Testing
Action: Test protective-earth resistance and touch/chassis leakage using the facility's Class I, Type BF procedure. These tests are specifically included after repair.
Expected outcome: Results meet applicable facility limits.
13. Final Inspection and Documentation
Action: Disconnect the test kit. Confirm a clear air path, secure hose/controller, installed filter/covers, clean dry surfaces, and no alarm or fault. Apply the PM label and document all results.
Expected outcome: The unit is complete, within specification, and ready for service.
Electrical Safety Testing
The Model 875 is Class I, Type BF equipment. The manual states that leakage meets IEC 60601-1 and UL 60601-1 requirements but does not give a universal field limit.
Ground resistance measured in ohms, expected ≤ 0.5 Ω or facility/NFPA 99 criteria if different.
Touch/chassis leakage measured in microamps:
Facility limit used =
Result =
Pass / Fail =
Pass / Fail Criteria
PM Pass Criteria
- Unit, mounting, air path, hose, controller, power connection, and ground pass inspection.
- Surfaces are clean and dry; filter is replaced and correctly installed.
- Calibration stabilizes at 43.0°C +/-0.5°C using the Model 90055 kit.
- OT indicator and alarm activate, heater shuts off within 2 minutes, and peak remains below 56°C.
- Alarm reset, cool-down, functional operation, and electrical safety pass.
Remove From Service Criteria
- Significant damage, insecure mounting, blocked airflow, fluid intrusion, or grounding defect remains.
- Approved test equipment is unavailable or calibration cannot meet 43.0°C +/-0.5°C.
- Any OT indication, alarm, shutdown-time, or peak-temperature criterion fails.
- An unresolved fault, abnormal noise, odor, overheating, or shutdown remains.
- Electrical safety fails or a required post-repair inspection is incomplete.
Copy/Paste CMMS Work Order Procedure
Use the manufacturer service manual, facility policy, and approved AEM program to determine the final PM interval and return-to-service requirements.