An Air Handling Unit failure is rarely sudden. Clogged filters, worn belts, fouled coils, stuck dampers, and degraded sensors each build up quietly over weeks — reducing air quality, increasing energy consumption, and eventually forcing a breakdown that disrupts the entire building. This AHU maintenance checklist covers every component that requires regular inspection, with frequency intervals validated against ASHRAE 62.1 and SMACNA standards. Use OxMaint's Preventive Maintenance module to convert this checklist into scheduled digital work orders that your team executes on mobile — no paper, no missed tasks.
Air Handling Unit (AHU) Maintenance Checklist with CMMS
Filters, belts, bearings, coils, dampers, sensors, drainage, and airflow — every AHU inspection point with frequency, acceptance criteria, and CMMS scheduling guidance.
Complete AHU Maintenance Checklist
Organized by component and frequency. Each item includes the acceptance criterion that determines pass or fail. All items are available as pre-built work order templates in OxMaint.
| Inspection Item | Method | Acceptance Criterion | Action if Failed |
|---|---|---|---|
| Supply air temperature | Read BAS setpoint vs actual | Within ±1°F of setpoint | Check coil valve, sensor calibration |
| Static pressure differential | Read BAS or local gauge | Within ±10% of design | Check filter loading, fan speed |
| Fan motor amp draw | Read panel or BAS | Within ±5% of nameplate FLA | Investigate belt, bearing, airflow restriction |
| Condensate drain — no backup | Visual inspection | Clear flow, no standing water | Clear blockage — raise WO if drain pan full |
| Inspection Item | Method | Acceptance Criterion | Action if Failed |
|---|---|---|---|
| Filter pressure drop | Magnehelic gauge or BAS | Below manufacturer final resistance rating | Replace filter — log in CMMS with part number |
| Filter visual condition | Remove and inspect | No bypass gaps, tears, or frame damage | Replace and seal frame correctly |
| Cooling coil visual inspection | Visual with flashlight | No visible biofouling, clean fins, no fin damage | Schedule coil cleaning — raise PM WO |
| Drain pan inspection | Visual and physical check | Clean, no algae, no scale buildup, proper slope | Flush and treat with biocide — log in CMMS |
| Condensate drain line flush | Pour water at pan, observe flow | Clear, unobstructed discharge | Rod/flush drain — confirm clear before close-out |
| Inspection Item | Method | Acceptance Criterion | Action if Failed |
|---|---|---|---|
| V-belt tension and condition | Deflection test — span midpoint | Deflection per OEM spec (typically 1/64" per inch of span) | Adjust or replace belt — CMMS part log required |
| Belt alignment — sheave check | Straight-edge across sheave faces | Parallel within 1/16" over 12" | Realign motor or fan sheave — log correction |
| Fan bearing lubrication | Grease per OEM spec — purge to displacement | No evidence of water ingress, discoloration | Increase grease frequency — check seal condition |
| Damper blade operation | Manual and actuator-driven stroke test | Full open/close without binding, correct linkage travel | Lubricate pivots — replace actuator if position error > 5° |
| Outside air damper seal condition | Visual inspection of blade edge seals | No visible gaps or torn seals when closed | Replace seals — log in CMMS with material cost |
| Fan wheel visual — blade condition | Open access panel — visual and tactile | No visible fouling layer, no blade cracks or erosion | Clean with non-corrosive solution — inspect for cracks NDT |
| Inspection Item | Method | Acceptance Criterion | Action if Failed |
|---|---|---|---|
| Cooling coil chemical cleaning | Coil cleaning solution — rinse toward drain | Fin face free of biofilm and debris — confirmed by airflow delta | Repeat cleaning — document before/after static pressure |
| Heating coil inspection and clean | Fin visual + compressed air blow-out | No visible blockage — heating valve response confirmed | Mechanical cleaning — check valve actuator modulation |
| Temperature and humidity sensor calibration | Calibrated reference instrument comparison | Supply air temp within ±0.5°F, RH within ±3% | Recalibrate or replace — log in CMMS with reading before/after |
| Airflow traverse — cfm verification | Pitot tube or anemometer traverse | Within ±10% of design airflow at current static | Adjust VFD speed, fix ductwork leakage — re-test after fix |
| Motor insulation resistance test | Megohmmeter at 500VDC | Insulation resistance > 1 MΩ (NEMA MG-1) | Plan motor rewind or replacement — do not restart if below 1MΩ |
| Inspection Item | Method | Acceptance Criterion | Action if Failed |
|---|---|---|---|
| Duct leakage test (supply and return) | Duct blaster or duct pressure test | ASHRAE 90.1 Class A: leakage < 4% of design airflow | Seal duct joints — re-test and document for compliance |
| Fan shaft and coupling inspection | Visual + runout measurement at coupling | Runout < 0.002" TIR — no visible corrosion on shaft | Replace shaft or coupling — laser align after replacement |
| Controls sequence of operation test | BAS functional test — all modes | All sequences perform per design intent — cooling, heating, economizer, occupied/unoccupied | Reprogram or recalibrate controls — document retest |
| Fire/smoke damper operational test | Actuate via test switch — verify closure and reset | Full closure within 10 seconds — reset confirmed per NFPA 80 | Replace damper or actuator — critical safety item — log in CMMS immediately |
Run This Checklist Digitally — Starting Today
OxMaint converts every item in this checklist into mobile work orders with auto-scheduling, technician signoff, and photo documentation. No paper, no missed tasks, and full ASHRAE compliance records generated automatically.
Expert Review
The failure pattern I see repeatedly in commercial building HVAC systems is not dramatic — it is the gradual accumulation of deferred maintenance items that each seem minor in isolation. A filter running 15% over its final resistance rating. A belt with 20% more tension variation than spec. A drain pan with light biofilm growth. Individually, none of these trigger a breakdown. Together over a 6-month period, they produce an AHU that consumes 28% more energy, delivers 15% less airflow than designed, and creates IAQ complaints that the building manager cannot explain because nobody has been tracking the component history. The checklist in this guide represents the minimum viable PM program for an AHU. Digitizing it in a CMMS like OxMaint is what converts an intention into a consistent, documented practice — which is what distinguishes facilities with 15-year AHU lifespans from those replacing units at year 8.
Frequently Asked Questions
Your AHU Checklist Belongs in a CMMS, Not a Binder
Paper checklists do not send reminders, do not escalate missed tasks, and do not build the asset history that ASHRAE compliance requires. OxMaint gives your team a mobile-first maintenance program that executes this entire checklist consistently — with full documentation generated automatically. Start free and have your first digital AHU inspections running this week.
