Your clean room's air changes are on the design sheet. Are they in the room?
The AHU was commissioned to deliver a fixed number of air changes per hour. Belts slip, filters load, dampers drift. Nobody knows until the audit — unless the room is logging CO₂.
Clean room · CO₂
CO₂ at 00:39
- Type
- CO₂ logger
- State
- Active
- Humidity
- 64% RH
- Last reading
- 23 Oct, 00:39
Fig. 1 — CO₂, last 1 h
Smart Logger in a pharmaceutical clean room: CO₂, temperature and humidity logged continuously, with the decay curve that reveals the real air-change rate.
Why the design ACH and the real ACH drift apart
A clean room's air-change rate is set once, at validation, by balancing the AHU and measuring at the grilles. From that day the number lives on a sheet. The equipment behind it — belts, filters, dampers, VFDs — is drifting from the first week.
A HEPA filter loading up raises resistance and the airflow falls. A fan belt slips and the fan does 90% of its speed. A fresh-air damper gets left half-closed after maintenance. Each one cuts the real air changes while every panel still reads normal, and the next time anyone measures is the next audit.
CO₂ is the tell. People working in the room raise it; fresh air brings it back down. The rate at which it falls when the room empties is a direct function of the ventilation rate. Log it continuously and the air-change rate is visible on a chart every day — and a drift shows up the same shift, not at the inspection.
From a logger to a defensible ACH record
Place a CO₂ logger
Wireless, battery-powered, placed in the room. It logs CO₂, temperature and humidity every few minutes to one screen — no wiring into validated systems.
Watch the decay curve
When the shift ends and the room empties, CO₂ falls at a rate set by the ventilation. A slower fall than last week is a loaded filter or a slipping belt — found the same day.
Then close the loop
SKW EnergyOS can run the clean-room AHUs autonomously: holding ACH, pressure cascade and humidity inside hard bounds while trimming fan energy, on the BMS you already have.
Logged continuously as the ventilation tracer
Humidity and temperature on the same logger
Between readings, 24×7
Nothing touches validated systems
Questions we get asked
Does CO₂ actually measure air changes?
It measures the ventilation rate — the fresh-air part of the air changes — through how fast CO₂ decays once the room empties. It is the standard tracer-gas method, running continuously instead of once a year.
Does this interfere with the validated AHU or BMS?
No. The logger is a standalone wireless device with its own screen. Nothing is connected to or written into the validated control system.
Can we use it for the audit?
The log is exportable per logger and per period — a continuous record of CO₂, temperature and humidity that sits alongside your periodic grille measurements.
What about temperature and humidity?
The same logger records both, so excursions in the room's environmental envelope are on the same chart as the ventilation tracer.
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