Aspirating smoke detection, usually shortened to ASD and often known by brand names such as VESDA, is the system of small bore pipes that draws air back to a very sensitive detector. You find it where ordinary point detectors struggle: data halls, high bay warehouses, cold stores, heritage interiors, cleanrooms and anywhere a false discharge of a suppression system would be expensive.
On 18 September 2026 the Fire Industry Association announced the 2026 Code of Practice for Aspirating Smoke Detection Systems, which it describes as “the first full revision of this important industry guidance since 2012”. The full 110 page Code is a free download and supersedes the February 2012 edition, which is withdrawn.
A code of practice is not law and it is not a British Standard. It sets out recommendations, and the Code itself warns that it “should not be quoted as if it were a specification”. But it is the reference designers, insurers and fire engineers will now reach for, so if you own or manage a building with ASD, it is worth knowing what has moved.
What has changed
The foreword lists the principal changes. The ones that matter to building owners are these.
It now lines up with BS 5839-1:2025. The 2012 Code predated two revisions of the fire alarm standard. It now cross refers throughout to the current edition, including on power supplies and on who is responsible for the system.
Warehouses get proper guidance. Following FIA sponsored research, the Code sets out five example schemes for high rack warehouses, from ceiling detection only through to multi level in rack sampling, and adds a design template that scores six risks and three mitigations to suggest which scheme fits. It is explicit that it is “not an exact science” and that the schemes are not prescriptive. The FIA publishes the template as a spreadsheet.
Data halls and high airflow. The FIA’s 2020 guidance on fire detection in high airflow environments is folded in. For electronic equipment areas the Code calls it “best practice” to use both primary detection (at the air handling unit return grilles) and secondary detection (at ceiling level), because the air handling units are not always running, for example during maintenance. It also flags battery energy storage as a growing risk in and around data centres.
Coincidence is not redundancy. A new passage clears up a confusion that shows up in a lot of suppression designs. Coincidence means two separate signals must agree before a suppression system releases. Redundancy means a backup keeps working if one part fails. The Code says plainly that using two detectors for coincidence “does not necessarily provide for redundancy”, and sets out four arrangements with their trade offs.
Other changes: new guidance on multi sensors within ASD, in cabinet detection and the flammability of sampling pipework; lift recommendations reviewed against European codes; an extended paper burn test for Class A and Class B systems in high areas; and updated product marking information covering CE and UKCA.
If your ASD triggers a gas suppression system
This is where the Code is most useful to owners, because an unwanted discharge empties the cylinders and leaves the room unprotected until they are refilled.
The Code’s position is clear on three points:
- Do not let an ASD release a suppression system on its own. “Direct triggering of an extinguishing system (without a suppression release panel) is not recommended”, because an ASD alone lacks the monitoring and integrity the job needs.
- Do not use two alarm levels from one detector as your coincidence. “Using multiple alarm thresholds based on the signal from a single ASD sensing element is not considered to provide coincident detection.”
- Keep the very sensitive signal for early warning. The high sensitivity thresholds of Class A and Class B detectors “should not be used for both inputs to a coincidence arrangement”.
The Code points to BS 7273-1 and the FIA’s own coincidence guidance for the release side. If your suppression cause and effect was designed years ago around a single ASD with a “pre alarm, fire 1, fire 2” ladder, it is worth having someone look at it against this section.
What it says about maintenance
The Code is blunt: ASD systems may be low maintenance, “they are not ‘no maintenance’”. It recommends maintenance “at least annually”, more often in dirty or dusty environments or where the risk assessment says so, and says the frequency and method “should be clearly documented and kept with the fire safety logbook”.
The detail matters. Where maintenance relies on performance readings rather than smoke at every hole, the Code gives typical tolerances: airflow within 20% of the commissioning value, and transport time from the furthest hole within 15% or 3 seconds, whichever is greater. That only works if the commissioning values were recorded. Where “the original commissioning time is not known”, the Code says every sample hole or group of holes must be tested individually, which in a high bay warehouse or a live data hall means access equipment, permits and downtime.
What to check this quarter
- Do you have the commissioning figures? Airflow, transport times, hole sizes and pipe layout drawings. If not, your maintenance visits cannot compare against a baseline.
- How is your suppression release arranged? Check that coincidence comes from two independent sources, not two thresholds on one detector.
- When was the design last reviewed against the building? The Code lists changes of use, layout, processes, air conditioning and even outside diesel fumes as things that can affect performance.
- Who is your responsible person for the system? The Code points to clause 47.1 of BS 5839-1:2025 and says the person should be trained to spot the environmental changes that affect ASD.
- Warehouses: if you have added racking height or density since installation, run the new design template against what you have.
How Gemini helps
We design, install and maintain aspirating detection as part of our fire alarm installation and service and maintenance work, including in critical zones at Peterborough Court. Where ASD triggers gas suppression, our suppression design and maintenance teams review the cause and effect as one system. We work across data centres, warehouses and heritage sites. If you are missing commissioning figures, we can re-baseline the system so every future visit has something to measure against. Talk to us.
Sources: FIA, ASD Code of Practice 2026 announcement; FIA, Design, Installation, Commissioning and Maintenance of ASD Systems Code of Practice, Version 2, September 2026 (PDF); FIA, warehouse ASD design considerations spreadsheet.
