DEVB TC(W) No. 3/2023, Annex A
4S components: what a Smart Site Safety System must include
A Smart Site Safety System (4S) has three parts under DEVB TC(W) No. 3/2023: smart safety devices, a communication network and a centralised management platform (paragraph 5). Annex A lists twelve device components, plus VR safety training. Kodifly supplies, installs and runs the set your site needs as one project.
The three parts, and the twelve components
Paragraph 5 of DEVB TC(W) No. 3/2023 says a Smart Site Safety System (SSSS, or 4S) generally has three components. They are smart safety devices that watch high-risk activities, a communication network that carries the data, and a centralised management platform that analyses data, raises alerts and supports follow-up.
Annex A is the sample Particular Specification. Since the memo of 10 July 2026 it lists twelve components in clause 5(12), from the centralised management platform to smart fire and smoke detection, and VR safety training in clause 6. Annex B sets out how each is measured, by the month, and Annex C is the sample Bills of Quantities.
Paragraph 9 lets a project team choose the devices that suit the works. The annexes are a sample, not a minimum and not a limit. The Construction Industry Council groups 4S products into ten main categories for its CITF product list.
The components in Annex A, clauses 5(12) and 6
The core requirement of each, in the circular's own numbers.
| Clause | Component | Core requirement |
|---|---|---|
| 5(12)(a) | Centralised management platform | Receives, records and displays alerts from every component. At least 30 concurrent users. Data kept for at least 3 months. |
| 5(12)(b) | Digitised tracking of plant, MEWPs, lifting appliances, lifting gears and powered tools | A unique digital ID on each item. Scan it to see certification, examination and maintenance records. Alert when overdue. |
| 5(12)(c) | Digitised permit-to-work | Online application, issue and tracking. Alert when a permit expires. |
| 5(12)(d) | Electronic lock and key access control | Locks on hazardous areas. Siren of at least 70 dB on forced or outdated-key opening. |
| 5(12)(e) | Mobile plant danger zone alert | Sensors for 360 degree cover. Danger zone generally at least 2 m. Siren of at least 100 dB. |
| 5(12)(e) | Tower crane lifting zone alert | Danger zone generally at least 7 m radius from the hook. Siren of at least 100 dB. |
| 5(12)(f) | Smart monitoring of workers | Indoor and outdoor location, standstill alert, body temperature and heart rate alerts. Vital sign values are not shown on the platform. |
| 5(12)(g) | AI safety monitoring | At least 80% true positive in the live test and 90% on average after four weeks. Alarm within 1 second. |
| 5(12)(h) | Confined space monitoring | Worker counting and tracking, and gas, oxygen and temperature readings with real-time alerts. |
| 5(12)(i) | MEWP smart monitoring | Proximity sensors. Siren of at least 70 dB and automatic stop inside the set distance (500 mm in the sample). |
| 5(12)(j) | Scaffolding putlog monitoring | Warning within 30 seconds of a wire-cut. Tension measured every 60 seconds. |
| 5(12)(k) | Smart fire and smoke detection | Alert within 30 seconds of an abnormality. Video from 1 minute before to 1 minute after. |
| 6 | VR safety training | Half-yearly training for workers in eight named high-risk activities. |
Rules that apply to every component
These sit outside the individual device clauses. Each one is a point an auditor can check.
Set up
- Submit the implementation plan within 14 days of the starting date or tender acceptance (clause 2(1)).
- Deliver every component within 1 month of the plan being accepted, unless agreed otherwise (clause 2(3)).
- Install and test within 5 working days of delivery (clause 2(5)).
- Provide a site network that supports mobile communication, and use more than one network system where needed (clause 4).
Every alert
- Reach at least 90% accuracy in detecting alert scenarios, proved by a live trial (clause 5(2)).
- Send each alert to the platform with person or machine ID, date, time and duration (clause 5(2)).
- Timestamp and encrypt data, make it available by API and stream it to the platform (clause 5(6)).
- Use cameras with protective casing, at least 1080 pixels and 5x optical zoom (clause 5(3)).
Every day and every month
- Check devices before work each day and record any irregularity (clause 5(8)).
- Keep an action plan with response times and named supervisors (clause 5(9)).
- Repair or replace within 24 hours of a reported fault (clause 5(5)).
- Report monthly to the Site Safety Management Committee (clause 5(11)).
- Hold 99.9% uptime in working hours and comply with the Personal Data (Privacy) Ordinance (clauses 1(2) and 1(3)).
How Kodifly delivers the set
One project, one team, one platform. We specify the components your risk assessment calls for, then supply, install and run them.
Software, devices and installation together
Platform and permit-to-work in SpatialSense
Electronic locks for hazardous areas
Plant and tool tracking
Mobile plant and tower crane alerts
Wearables for workers
AI cameras
Confined space monitoring
MEWP, putlog and fire detection
Monthly 4S report from the platform record
Link to the DWSS hub
4S components, answered
What are the components of a Smart Site Safety System?
Three parts under paragraph 5 of DEVB TC(W) No. 3/2023: smart safety devices for high-risk activities, a communication network for the data, and a centralised management platform for analysis, alerts and follow-up. Annex A, clause 5(12), lists twelve device components.
How many 4S components does Annex A list?
Twelve in clause 5(12), plus VR safety training in clause 6. The memo of 10 July 2026 added smart monitoring for MEWPs, smart monitoring for scaffolding putlogs, and smart fire and smoke detection.
Must a contract use every component?
No. Project teams select suitable devices for the nature of the works and the high-risk activities involved, and are not limited to the annexes (paragraph 9).
What accuracy must a 4S alert reach?
Any component that issues automated warnings must reach at least 90% accuracy in detecting its scenarios, proved by a live trial (clause 5(2)). AI safety monitoring must also pass a test of at least 80% true positive and then average 90% (clause 5(12)(g)).
What does 4S cost?
The estimated cost would normally not exceed HK$10 million or 1% of the estimated contract sum, whichever is lower (paragraph 10). The contractor bears servicing, repair and consumables (clause 3(1)).
Related guides
Plan the 4S set for your site
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