Match the airflow direction
Orient and position sampling holes where smoke-laden air will pass. Manufacturer guidance is a starting point; the installed arrangement requires functional validation.
Application · Clean rooms and controlled environments
Very early fire detection for clean rooms
Clean-room ASD must be designed around airflow, pressure and process aerosols. Sampling can be placed in return air, the protected space or equipment exhaust, but direction, materials, maintenance and thresholds must be validated against the clean-room class, HVAC modes and production process.
Risk conditions that
change the design
The sampling network must respond to the real environment and operating modes.
- 01Rapid smoke dilution caused by high air-change rates
- 02Laminar flow changing the smoke path
- 03Maintenance introducing contamination
- 04Process aerosols causing non-fire particulate events
Design priorities
Resolve these conditions before model and network confirmation.
Check shutdown conditions
A return-air strategy may lose its preferred response when HVAC stops. Define standby, cleaning and incident requirements.
Control materials and maintenance
Pipe materials, seals, filter replacement and test methods must comply with clean-zone procedures.
Characterise process interference
Separate combustion aerosols from process vapour, cleaning particles and normal production background.
Protection layers
Each layer should have a defined detection and response purpose.
Return-air sampling
In unidirectional-flow spaces, smoke may travel towards low-level or side return air. Sampling must match the real return path and equipment obstruction.
Ceiling or room sampling
Can complement return air during shutdown or abnormal modes, but smoke should not be assumed to move against laminar flow.
Equipment-level sampling
High-value or enclosed process equipment can receive local protection when exhaust, material compatibility and maintenance permission are confirmed.
Clean maintenance boundary
Pipe, seals, filter work, test aerosol and tool entry must follow the controlled-area maintenance procedure.
Inputs required before design
These inputs turn an application concept into an auditable technical decision.
| Parameter | Why it matters | Design output |
|---|---|---|
| Clean-room class and production state | Controls materials, entry, testing and maintenance. | Installation and service procedure |
| Air changes, flow pattern and pressure cascade | Determines smoke dilution and actual travel direction. | Room and return-air strategy |
| HEPA, FFU and return-air positions | Shows where particles can be sampled before filtration. | Hole elevation and direction |
| Process aerosol and cleaning activity | Identifies non-fire particles affecting the baseline. | Threshold and test conditions |
| Equipment exhaust and local risks | Determines whether equipment-level sampling is required. | Local protection scope |
| HVAC shutdown and incident modes | Return-air protection may change outside production. | Complementary detection and interface strategy |
Candidate models
A candidate remains provisional until project inputs and approval scope are reviewed.
Questions to resolve
Use these in the first project workshop.
- 01What are the clean-room class, air-change rate, pressure cascade and flow pattern?
- 02How does HVAC operate during standby, cleaning and incident modes?
- 03Which materials and tools are permitted during installation and service?
Common questions
Why do clean rooms need very early fire detection?
High-value equipment and continuous production make early intervention important, while high air-change rates dilute smoke quickly. ASD can sample return or process airflow directly, but process-particle interference and clean maintenance must be controlled.
Which direction should a clean-room sampling hole face?
It should face or intersect the actual smoke-laden airflow. Any suggested angle is only an initial design condition; laminar flow, return positions and a representative smoke test determine the final orientation.
Should a clean room use ASD 531 or ASD 532?
ASD 531 can be screened for a small clean space or local equipment. ASD 532 is generally evaluated when a medium high-air-change space needs a lower pre-signal threshold, higher suction pressure or Ethernet connectivity.
Source and review record
Manufacturer facts: SECURITON SecuriSmoke ASD Product Brochure V2.0 EN and current manufacturer design documentation. Application sequence and candidate-model guidance are PEIEN engineering recommendations.
Last reviewed: 27 July 2026. Project values remain assumptions until reviewed by a suitably qualified fire professional or experienced ASD practitioner.
Apply the guidance to your project.
Submit the destination country, application, area, environment, drawings and project stage for a first selection review.