Early Fire Detection in the Server Room: Why Aspirating Smoke Detectors are the Standard

Why Smoke Detectors in Server Rooms Often React Too Late 

Strong air currents dilute smoke and carry it past the detector

Data centres have defined airflow directions – supply air, return air, hot aisle, cold aisle. As a result, smoke is often carried away or swirled so vigorously that it does not reach the ceiling in sufficient concentration. Yet that is precisely where conventional point-type smoke detectors are installed. The result: The smoke detector in the server room reacts with a delay – or not at all.

Raised floors and cable routing shift the points of origin

Many critical incidents begin beneath the raised floor – at cable bundles, power distribution units (PDUs), or cable transitions. Others start directly in the rack: at power supplies, connectors, or overloaded electronics. In such cases, a ceiling-mounted detector may respond too late, especially if smoke is drawn away via the return air duct before it spreads throughout the room.

Cold aisle/hot aisle – smoke develops where the detector does not measure

In the cold aisle, cooled air is specifically supplied; in the hot aisle, heated air is extracted. Smoke that develops often moves with the airflow toward the return air duct instead of spreading evenly throughout the room. This means: delayed alarms, higher risk of downtime, and consequential damage.

What is an Aspirating Smoke Detector? 

Definition and Basic Design

An aspirating smoke detector is an active smoke detection system. Air is continuously drawn from monitored areas through a network of pipes with defined intake openings and directed to a central evaluation unit. There, highly sensitive particle sensors analyse the air sample for smoke components.

Typical components:

• Duct network with rigid ducts or capillaries, depending on the zone
• Intake openings (sampling points) at defined locations
• Evaluation unit with detection, alarm levels, and fault monitoring
• Filter and airflow monitoring for stable measurement conditions

Operating Principle – from Sampling to Particle Analysis

      1. A fan continuously draws air through multiple sampling points.
      2. The air is conditioned and filtered in the evaluation unit.
      3. The sensor system evaluates the particle or smoke concentration.
      4. Depending on the threshold value, multiple alarm levels are triggered – e.g., pre-alarm and main alarm.

Why this is an advantage in the data centre

• Measurements are taken where smoke is most likely to appear first – raised floors, near racks, and return air areas.
• Smoke is reliably detected even at high air exchange rates.
• The central evaluation unit simplifies inspection and maintenance without having to access each point detector individually in sensitive areas.

EN 54-20 – Understanding Classes A, B, and C

EN 54-20 classifies aspirating smoke detectors based on their sensitivity. For planners and operators, this standard serves as a key basis for selecting the appropriate solution for early fire detection in the data centre.
 

Class A – Very High Sensitivity

Designed for very early detection. Suitable for highly critical IT environments where even the smallest smoldering events must be detected – such as in areas with particularly high availability requirements.

Class B – High Sensitivity

Typical for many professional applications where early detection is important, but constraints such as airflow, dust levels, and maintenance concepts are taken into account in a balanced manner.

Class C – Standard Sensitivity

Recommended when requirements are less stringent or environmental conditions suggest a more robust design.

Selection Guide for Server Rooms and Data Centres

In practice, the following questions are crucial for selecting the appropriate class:

• How early should detection occur – already in the smoldering phase or only when smoke is visible?
• What are the airflow patterns and return air circulation like in the specific facility?
• Which zones are particularly critical – raised floor, rack level, ceiling?
• What are the applicable framework conditions – e.g., requirements from standards, insurers, or the project context (including VdS 6003)?

The specific design – pipe lengths, hole patterns, zone division – depends on the planning and should comply with standards.

Schrack Seconet – Aspirating Smoke Detectors and Integration into the Fire Alarm System

Schrack Seconet offers aspirating smoke detectors in its portfolio that are designed for demanding environments such as data centres, industrial buildings, and critical infrastructure. For operation in data centres, integration into the fire alarm system (FAS) is crucial in addition to detection performance: Alarms, fault messages, and the control of additional fire protection functions are consistently mapped within the overall system – for example, via the Integral EvoxX fire alarm system.

In high-performance computing environments such as the LUMI supercomputer, Schrack Seconet relies on a coordinated overall concept comprising fire detection technology, fire suppression system control, and remote monitoring. Early fire detection via aspirating smoke detectors can be a component within such projects – depending on the protection objective and facility requirements.