Understanding EN54-20 Aspirating Smoke Detection Sensitivity Classes


Among the many innovations in fire detection over recent years, aspirating smoke detection stands out for its unparalleled sensitivity and early warning capabilities. Unlike traditional fire detectors, aspirating systems excel in detecting minute traces of smoke particles, offering swift responses and heightened protection.

Discreet and reliable, aspirating systems have transformed fire safety engineering, ensuring enhanced vigilance in diverse environments and allowing installers to provide world-class fire detection solutions for buildings where traditional fire detection may prove problematic or disrupt the aesthetics of the structure.

How does Aspirating Smoke Detection work?

Unlike traditional fire detectors which detect the presence of smoke in their immediate vicinity only, aspirating smoke detection works by continuously drawing in air from the protected environment through a network of pipes. This air is then passed through a sensitive detection chamber that can identify even tiny particles of smoke. If smoke is present in the air sample, the detector triggers an alert allowing a potential fire to be investigated.

Aspirating Smoke Detection at Eurofyre

Eurofyre have long been proponents of aspirating smoke detection, and are pleased to support the VESDA-E, VESDA, FAAST and ICAM brands of aspirating smoke detectors.


Part of the broader EN54 European Standards for fire detection originally published in 2006, EN54-20 pertains directly to aspirating smoke detectors (ASDs) and specifies requirements and test methods for their performance in fire detection and alarm systems. 

Compliance with EN54-20 ensures that aspirating smoke detectors meet prescribed quality and performance standards concerning sensitivity and operational reliability, providing assurance of their effectiveness in early detection of fires and minimising the risk of false alarms.

As part of EN54-20, aspirating smoke detectors are segmented into three sensitivity classes based on their detection capabilities.

Aspirating Smoke Detection Sensitivity Classes

The sensitivity classes outlined in EN54-20 help system designers and installers to select the appropriate ASDs based on the unique demands and risk profiles of their applications, ensuring effective fire detection while mitigating the likelihood of false alarms. The sensitivity levels of each class are not explicitly defined in measurable values, rather they provide a general indication of a detector’s sensitivity.

Class A – Very High Sensitivity

Class A aspirating smoke detectors achieve the highest sensitivity level and are capable of detecting minute concentrations of smoke particles in their air samples. Class A aspirating detectors are ideal for use in environments where early detection is critical, the goal being to detect and mitigate the fire risk before any damage is incurred, such as clean rooms and data centres, or when protecting high-value or irreplaceable goods. 

Class B – Enhanced Sensitivity

Well-suited for environments which require moderate sensitivity, Class B aspirating smoke detectors are able to detect a wide range of smoke concentrations and are suited to areas where there is some tolerance of false alarms, such as retail property, commercial buildings and hotels.

Class C – Normal Sensitivity

Representing the lowest sensitivity level, yet still capable of detecting smoke effectively, Class C sensitivity aspirating smoke detectors are commonly deployed in industrial settings and semi-outdoor applications like car parks where there is a higher likelihood of contamination and background smoke levels.

Typical Aspirating Smoke Detector Sensitivity Ranges

VESDA-E VEP Aspirating Smoke Detector

  • Backward compatible with existing VESDA installations
  • Multi stage filtration and optical protection
  • Wide sensitivity range
  • Smart on-board filter
  • Autolearn smoke and flow

Xtralis VESDA-E VEP aspirating smoke detectors offer four alarm levels and a wide sensitivity range covering all three sensitivity classes outlined in EN54-20. Capable of delivering Class A, B or C aspirating smoke detection, VESDA-E VEP detectors are available in single or four-pipe variations making this range of detectors suitable for a variety of applications.

VESDA-E VEP detectors achieve consistent performance over their lifetime via absolute calibration. Built on Flair Detection Technology, the VEP range provides continual detection performance and offers multi-stage filtration, absolute calibration and optical protection with clean air barriers. 

In order to achieve the required sensitivity class, pipe calculations should be carried out in order to determine the exact sensitivity and a maximum number of sampling holes applies:

Class AVEP-A00-1P: 30 holes
VEP-A00-P: 40 holes
VEP-A10-P: 40 holes
Class BVEP-A00-1P: 40 holes
VEP-A00-P: 80 holes
VEP-A10-P: 80 holes
Class CVEP-A00-1P: 45 holes
VEP-A00-P: 100 holes
VEP-A10-P: 100 holes

FAAST FLEX Aspirating Smoke Detector

  • One or Two-channel Version Available
  • Out-of-the-Box Operation
  • Bluetooth Interface
  • Modular Design
  • Field-Replaceable Components

Innovative FAAST FLEX aspirating smoke detectors can be configured to suit all three sensitivity classes and allow a high degree of flexibility through pre-engineered pipe network design and out-of-the-box operation. 

Built-in configuration and control mechanisms can be configured without the need for specialist tools and even offer extended configuration options and rapid diagnostics via a Bluetooth interface and associated smartphone applications. 

Serving a wide range of applications, the one-channel version of FAAST FLEX is designed to protect an area up to 1600m² while the two-channel variant is designed to protect areas up to 2000m².

Class ASingle Channel: 5 holes
Dual Channel: 8 Holes
Class BSingle Channel: 15 holes
Dual Channel: 28 holes
Class CSingle Channel: 32 holes
Dual Channel: 56 holes

VESDA VLF Aspirating Smoke Detector

  • Laser-based absolute smoke detection
  • Very early warning of a potential fire incident
  • Wide sensitivity range
  • Dual stage dust filtration
  • Programmable alarm thresholds

Xtralis VESDA VLF Aspirating Smoke Detectors provide superior very early warning, air-sampling smoke detection and features a unique Smoke Dial™ display that gives the user an instant understanding of a smoke event.

The Smoke Dial™ features a circular LED display to provide a visual indication of smoke growth and alarm conditions, even from a distance. In fault conditions, Smoke Dial™ doubles as an innovative ‘fault finder’ feature; a smart diagnostic tool that provides the detector’s status without the need for evaluation tools or additional programming.

VESDA VLF-250 can support a single pipe run up to 25m, or 2 branches of 15m each. VLF-500 detectors can support a single pipe run of 50m, or 2 branches of 30m per branch.

Class AVLF-250: 12 holes
VLF-500: 30 holes
Class BVLF-250: 12 holes
VLF-500: 30 holes
Class CVLF-250: 12 holes
VLF-500: 30 holes

Why Choose Eurofyre?

Honeywell Fire Platinum Partner
Eurofyre is a Honeywell Fire Platinum Partner. This means we can offer regional or industry-specific solution expertise that includes implementation and advanced customer support for models for Honeywell products, including VESDA, VESDA-E, FAAST and ICAM aspirating smoke detection, along with the most competitive pricing.
Complete System Supplier
Eurofyre is a complete system supplier and has been a major Xtralis technical wholesaler since 2007. This means we can offer expert advice and supply all aspects of fire detection including aspirating smoke detection systems, conventional and addressable fire alarm control panels and linear heat detection.
Pipework Design
Eurofyre can also provide assistance with aspirating pipe network design to ensure optimum network performance and installation quality.
Demonstration and Training
We have a sophisticated training facility where we offer demonstrations and expert training on a range of systems, including a comprehensive selection of Xtralis aspirating smoke detection systems.
After-Sales Support
Eurofyre prides itself on providing after-sales care and support that is second to none. We offer both on-site and telephone assistance to help you ensure that your system is fully operational and working at its best.

For more information about Aspirating Smoke Detection, or to discuss any of the other products that Eurofyre has to offer, please feel free to get in touch either by phone on +44 (0) 1329 835 024, by email to [email protected] or via the online enquiry form situated on our contact page.

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