Operating rooms carry the strictest ventilation rules in any hospital, and missing them is a patient safety risk, not a paperwork one. ASHRAE 170 sets a hard floor for OR air changes, outdoor air, pressure differential, and filtration, while NFPA 99 ties that floor directly to Medicare eligibility and Joint Commission survey outcomes. Most facilities still track these readings on paper rounds sheets that sit in a binder until a surveyor asks for a full year of history at once. A missed pressure log looks identical to an actual ventilation failure during inspection. Oxmaint's hospital CMMS software turns OR ventilation compliance into a continuous, automated record instead of a pre-survey scramble — book a demo to see it running against your own OR data.
Hospital CMMS
ASHRAE 170 / NFPA 99
2026 Edition
OR Ventilation Benchmarks
The Four Numbers Every OR Must Hit, Every Hour
20 ACH
Minimum total air changes per hour required in every operating room
4 ACH
Of those 20, at least four must be fresh outdoor air, not recirculated
+0.01 in.wg
Minimum positive pressure the OR must hold against every adjoining space
MERV 16
Minimum filter efficiency on OR supply air, HEPA in higher-risk procedure rooms
Facilities running 20+ ACH consistently cut airborne bacterial counts by roughly 90% versus low-ACH rooms — and doubling ACH drops particle concentration to about a quarter of its starting level.
Why It Keeps Failing
Paper Rounds Sheets Cannot Survive a Real Survey
Paper & Spreadsheet Tracking
Technician walks the OR wing and writes pressure readings by hand
Gauge drift or a stuck reading goes unnoticed for days
Twelve months of logs reconstructed the night before survey
Filter change dates live in a different binder than pressure logs
One missing entry reads as a compliance failure, not a clerical gap
Oxmaint OR Ventilation Module
ACH, pressure differential, and humidity logged continuously against each room asset
Out-of-range pressure triggers an alert before a case is scheduled in that room
Twelve months of records exportable as a survey-ready package in minutes
Filter, PM, and pressure history linked under one OR asset record
Every reading timestamped and attributed to the technician who took it
ASHRAE 170 Reference
Core OR Ventilation Parameters and How They Are Tracked
| Parameter | ASHRAE 170 Requirement | Why It Matters | Tracked In Oxmaint As |
|---|---|---|---|
| Total Air Changes | Minimum 20 ACH | Dilutes and removes airborne surgical site infection risk | Scheduled sensor or manual reading, logged per room |
| Outdoor Air Changes | Minimum 4 ACH of the 20 total | Prevents recirculated air from concentrating contaminants | Linked to AHU asset and outdoor air damper PM |
| Room Pressure | At least +0.01 in.wg positive to adjacent spaces | Keeps corridor and prep-room air from entering the sterile field | Continuous log with automatic excursion alert |
| Filtration | MERV 16 minimum, HEPA for high-risk procedures | Removes particulates before they reach the surgical zone | Filter change work order tied to asset lifecycle |
| Temperature & Humidity | Facility-defined range per room function | Supports staff comfort and equipment sterility limits | Rounds checklist field with min/max threshold alert |
Stop Reconstructing Twelve Months of OR Logs Overnight
See your operating rooms' ACH, pressure, and filtration history in one dashboard, ready for the next Joint Commission or CMS survey before it is even scheduled.
Platform Capabilities
How Oxmaint Automates OR Ventilation Compliance
Continuous Pressure & ACH Logging
Manual rounds or connected sensors feed readings straight into the room's asset record, replacing rounds sheets with a searchable history.
Excursion Alerts
A pressure or ACH reading outside range notifies facilities staff instantly, before a surgical case is booked into that room.
Filter & PM Scheduling
MERV and HEPA filter changes are scheduled against real usage and linked to the AHU serving each OR, so nothing is tracked separately.
One-Click Survey Package
Generate a full twelve-month, chapter-organized NFPA 99 documentation package for surveyors in minutes instead of days.
Risk Category Mapping
Every OR, isolation room, and procedure space is tagged to its NFPA 99 risk category so the right test frequency applies automatically.
Mobile Rounds Checklists
Technicians complete digital ventilation rounds from a phone or tablet, with signature capture and timestamped submission.
Getting Started
From Paper Binder to Survey-Ready in Three Steps
Step 1
Map Your OR Assets
Import every OR, AHU, and pressure-monitored space into Oxmaint and assign each its NFPA 99 risk category and ASHRAE 170 target values.
Step 2
Digitize Rounds & Alerts
Replace paper rounds sheets with mobile checklists and set excursion alerts for pressure, ACH, humidity, and filter life on every room.
Step 3
Export Survey-Ready Reports
Pull a complete, timestamped compliance package by chapter and risk category whenever CMS, Joint Commission, or your own EOC audit calls for it.
From Facilities Teams
What Hospital Engineering Leaders Say
Our worst survey findings were never actual ventilation failures — they were gaps in the paper trail. Once every OR pressure reading was logged automatically, the documentation gap closed and our EOC audits stopped flagging things we had actually done correctly.
Regional Acute Care Hospital, 240 Beds
We used to spend three days before every Joint Commission visit pulling twelve months of pressure logs from four different binders. Now that report exports in under ten minutes, and our team spends that time on actual preventive maintenance instead.
Multi-Campus Health System
Bring Every OR Under One Compliance Dashboard
Oxmaint gives facilities, biomed, and compliance teams a single view of ACH, pressure, humidity, and filtration status across every operating room, sourced from one platform.
Frequently Asked Questions
OR Ventilation Software — Common Questions
What ACH and pressure levels does an operating room need under ASHRAE 170?
An OR needs a minimum of 20 total air changes per hour, at least 4 of which are outdoor air, plus a minimum positive pressure of +0.01 in.wg against adjoining spaces. Book a demo to see these thresholds mapped against your own rooms.
How does NFPA 99 relate to ASHRAE 170 for hospital surveys?
CMS enforces ASHRAE 170 ventilation standards through its adoption of NFPA 99 for facilities built or modified since July 2016, and Joint Commission surveyors check the same pressure and ACH values during accreditation visits.
What documentation do surveyors actually request for OR ventilation?
Surveyors typically request up to twelve months of continuous pressure, ACH, and filtration records for every Category 1 and 2 space, organized by room and by system. Start a free trial to build that history automatically.
Can Oxmaint work with existing building automation or pressure sensors?
Yes — readings can be entered manually through mobile rounds checklists or fed in from connected sensors and building automation, and both flow into the same asset-level history and alerting.
Does OR ventilation software help outside of operating rooms too?
The same pressure and ACH tracking applies to isolation rooms, sterile storage, pharmacies, and any of the 60-plus space types ASHRAE 170 regulates. Book a demo to see it across your full facility.
Your Next Survey Starts With Today's OR Readings
Every hour an operating room runs outside ASHRAE 170 range is a risk you can catch immediately instead of finding out at survey. Oxmaint logs it, alerts on it, and documents it for you.
