Clean rooms
Cleanroom: ducts and particle classification, what to check
The duct never touches the cleanroom air: the terminal filter sits between them. Even so, a dirty duct can end in a count outside its class.
By Limpieza de Ductos Panamá
It is checked by crossing three data points: the particle count at rest and in operation, the pressure drop across the terminal filter and what the camera shows in the run before the filter. If the count rises in operation, the filter pressure drop has grown and the duct upstream is loaded, the duct is the likely cause. If the filter leaks at the frame or gasket, the problem is the filter.
Particle classification and the role of the duct
A cleanroom classification is a count: particles of a given size per cubic meter, measured at rest and in operation. The FDA guidance on aseptic processing equates ISO 5 with the old Class 100, ISO 7 with Class 10,000 and ISO 8 with Class 100,000, and notes that for an ISO 8 room a minimum of 20 air changes per hour is typically accepted, with much higher rates in the cleaner classes.
The duct does not deliver air to the room. It delivers air to the terminal filter, and the filter decides what gets through. A HEPA filter can theoretically retain at least 99.97 % of particles of 0.3 microns, according to the EPA. That is why dust traveling inside the duct does not reach the room while the filter is intact. What it does is load the filter faster, raise its pressure drop and lower the airflow. Less airflow means fewer air changes, and fewer air changes mean slower recovery and higher counts when people are working.
Dirty terminal filter or dirty duct: how to tell them apart
| Observation | Points to the filter | Points to the duct |
|---|---|---|
| High count at a single point under one filter | Leak at the gasket or filter media | Unlikely |
| High count across the room in operation, normal at rest | Possible if all filters are loaded | Likely, from reduced airflow across the whole branch |
| Filter pressure drop above the manufacturer maximum | Filter at the end of its life | Frequent cause: duct dust loaded it ahead of time |
| Failed filter leak test | Yes | No, unless the duct damaged the frame |
| The camera shows loose dust or moisture before the filter | No | Yes, and cleaning comes before changing the filter |
The FDA recommends HEPA filter leak tests at installation and then at suitable intervals, for example twice a year in an aseptic processing room, and also monitoring velocity uniformity across the filter face. If those tests are current and pass, and the count keeps rising in operation, the place to look is upstream. The camera inside the duct shows whether the run before the filter is loaded, damp or has open joints.
Behind this guide is Climatiza, an inspection and duct cleaning service, which always starts from the real condition of the system before proposing any work in clean rooms.
Signs in the particle count
- Counts in operation creeping toward the class limit month after month, with the same procedures and the same staff.
- Longer recovery time after an intervention in the room.
- Pressure differential to the corridor dropping with no change in doors or airlocks.
- Terminal filters reaching their maximum pressure drop sooner than the history shows.
- Prefilter gauge on the air handler rising fast after each change.
- More particles at the sampling points farthest from the air handler.
Inspection sequence without losing the classification
- Review records before opening anything. Counts, differentials, pressure drops and leak test dates. The sequence depends on what that history says.
- Inspect with the camera from outside the classified area. Entry is through duct access panels in the technical ceiling or at the air handler, without opening the room ceiling or touching the terminal filter.
- Clean the upstream run with the branch isolated. Dampers closed on the branch in question and the room out of operation according to the plant procedure.
- Change or certify terminal filters afterwards, never before. A new filter under a dirty duct loads just as fast.
- Requalify. Count, airflow, differentials and leak test by whoever certifies the room, with the duct report as an annex.
What to document for the cleanroom client
The room operator has its own certification file, and what it needs from the duct provider is material that fits there without interpretation. The report follows the order of the inspection and uses the branch and filter codes the plant already handles, as is done in other plants with controlled process areas and in technical rooms with dust sensitive equipment.
- Branch drawing with the inspected and cleaned sections marked.
- Camera photos before and after each section, with date and code.
- Pressure drop reading of prefilters and terminal filters on the day of the visit.
- What was not touched: terminal filters, room ceiling, airlocks.
- A recommendation on the interval for the next look, based on what was seen and not on a fixed calendar, as the technical guide explains.
A cleanroom with current filters and inspected ducts still needs its periodic count. What changes is that, when a count moves, the cause is found in the first place anyone looks.
To ask about availability or request a camera inspection, the Climatiza website lists the ways to contact the team and the duct cleaning service page explains how the work is organized.
Sources
On this site
- Industry and logistics parksHow the work is organized in this sector
- Data centers and server roomsA neighboring sector
- Camera inspectionThe real condition before deciding
Climatiza and Radar Panamá
Frequently asked questions
Can cleaning the duct contaminate the cleanroom?
It can, if done with the room in operation or without isolating the branch. That is why the sequence isolates the run, works from outside the classified area and leaves the terminal filter change or certification for later. Requalification closes the process.
How often is a cleanroom duct inspected?
When the records call for it: filters loading sooner than usual, counts rising in operation or slow recoveries. A fixed interval without that data has no basis, and the camera confirms without opening the room.
Does the terminal filter protect the room even if the duct is dirty?
While it is intact and within its pressure drop, it does retain the particles. The effect of a dirty duct is indirect: it loads the filter, reduces airflow and lengthens recovery. That is why the count in operation is the sign to watch.
Who certifies the room after the cleaning?
The certification provider the plant already uses, with its own counting equipment and leak tests. The duct report is delivered as an annex to that certification, not in its place.
Keep reading
Request an inspection
Do you want to know the condition of your system?
A camera inspection lets you see the inside of the ducts before deciding what to do. Message us and we will confirm availability.
- +507 6388-2083
- info@climatizapanama.com
- Calle Gervasio García, 8, Panama City