DEVB TC(W) No. 3/2023, Annex A
4S technical compliance matrix: how contract specifications differ
Hong Kong contract specifications for the Smart Site Safety System (4S) follow the sample in DEVB TC(W) No. 3/2023, Annex A, but they are not all the same. Some list 12 components and others 9, and the camera count, siren level, danger zone wording and data duties change. Kodifly's 4S meets both versions, clause by clause.
Last updated
- Components
- 12 in the sample, 9 in some contract specifications
- AI cameras
- At least 2, or at least 15
- AI alarm siren
- At least 70 dB, or at least 100 dB
- VR training activities
- 8, or 6
- Extra data duties
- OpenAPI v3 API, single sign-on, SFTP data hub, 99.99% redundancy plan
- Kodifly
- Meets both versions
Why the same 4S reads differently between contracts
Annex A of DEVB TC(W) No. 3/2023 is a sample Particular Specification. Paragraph 9 lets each project team choose the devices that suit the works, so drafters adapt the sample. A bidder answers the version in the tender, not the circular, and is scored against it in a technical compliance matrix.
Recent Hong Kong public works contract specifications follow two broad patterns. The first keeps the sample as it stands since the memo of 10 July 2026: 12 components in clause 5(12), including MEWP smart monitoring (i), scaffolding putlog monitoring (j) and smart fire and smoke detection (k). The second lists 9: the platform and eight device systems. It adds ladders, raises the camera count and siren level, and makes the danger zones hard minimums.
So the component count is 12 in the sample, 9 in some contract specifications. The second pattern also adds data duties in a separate schedule. The tables below set out each difference.
Where the two versions differ
Clause numbers follow Annex A. Both versions keep 99.9% uptime, 30 concurrent users, 3 months of storage and the 80% and 90% AI accuracy tests.
| Item | Sample-based specifications | Some contract specifications | SpatialSense |
|---|---|---|---|
| Components, 5(12) | 12, including MEWP (i), putlog (j) and fire (k) | 9: the platform plus eight device systems | Meets both |
| Tracking, 5(12)(b) | Site plants, MEWPs, lifting appliances, lifting gears and powered tools | Site plants, powered tools and ladders | Meets both |
| Permit list, 5(12)(c) | Includes use of MEWP | Includes use of ladder for work above ground | Meets both |
| AI cameras, 5(12)(g)(i) | At least 2 | At least 15, with edge and cloud processing | Meets both |
| AI alarm siren, 5(12)(g)(xii) | At least 70 dB, or higher if agreed | At least 100 dB | Meets both |
| Lock alarm, 5(12)(d)(iii) | Siren of at least 70 dB and/or flashing red light | Siren of at least 70 dB and flashing red light | Meets both |
| Danger zones, 5(12)(e) | In general not less than 2 m (plant), 7 m (hook) and 3 m (clearance) | In no case less than 2 m, 7 m and 3 m | Meets both |
| Confined space, 5(12)(h) | Includes PPE, breathing apparatus and qualification checks before entry | Worker count, location and air readings without the entry-check item | Meets both |
| Unsafe scenarios, 5(12)(g)(ix) | Includes smoking on site | Smoking not listed | Meets both |
| VR training, clause 6 | 8 activities, including working at height and near mobile plant | 6 activities | Meets both |
| Data duties | Timestamped data available by API (5(6)) | Adds OpenAPI v3 API, single sign-on, SFTP data hub, audits and data destruction | Meets both |
Extra duties some contract specifications add
Each is a scored line in the compliance matrix.
Integration
- A RESTful API with a valid OpenAPI v3 descriptor in JSON, standard create, read, update and delete operations, and documented errors.
- Single sign-on with OpenID Connect or OAuth2 against the main contractor's Azure Active Directory, using the Authorization Code flow with PKCE and the Client Credentials flow.
- An SFTP data hub that pushes raw data files to the contractor's server from whitelisted IP addresses, checked by an end-of-file CRC.
- Links from the platform to the DWSS and to DEVB's SmartEye dashboard.
Assurance
- A redundancy plan, with a report, for 99.99% availability.
- An independent security risk assessment and audit, and a privacy impact assessment under the Personal Data (Privacy) Ordinance.
Devices
- Smart locks with at least 6 months of battery, fail-secure locking, an offline whitelist and a low-battery alert below 20%.
- Wearables with at least 48 hours of battery, man-down detection and an SOS button.
- QR code or UHF RFID tags with offline scanning in underground or blind areas.
End of contract
- All data returned to the Project Manager, copies and backups securely destroyed, and a certificate of data destruction issued.
How Kodifly answers either version
Both versions, one project
Clause-by-clause compliance matrix
12 or 9 components, as the contract lists
Ladder and MEWP permits and tracking
AI cameras with edge and cloud processing
Sirens set to 70 dB or 100 dB
Danger zones set as hard minimums
OpenAPI v3 API, SSO and SFTP data hub
Data return and destruction certificate
4S contract variants, answered
What is a 4S technical compliance matrix?
A table in the tender that lists each 4S requirement with its clause and asks the bidder to confirm compliance and attach evidence, such as datasheets or test reports. It follows the contract's own version of Annex A of DEVB TC(W) No. 3/2023.
Why do some contracts list 9 components and others 12?
The sample in Annex A has listed 12 since the memo of 10 July 2026, adding MEWP, putlog and fire monitoring. Paragraph 9 lets teams select devices for the works, so some contract specifications keep 9 and leave those three out.
How many AI cameras must a 4S have?
The sample asks for a sufficient number to cover the site and not less than 2 (clause 5(12)(g)(i)). Some contract specifications set at least 15, with edge and cloud processing. SpatialSense meets either.
How loud must the AI camera siren be?
At least 70 dB, or a higher level as agreed, in the sample (clause 5(12)(g)(xii)). Some contract specifications ask for at least 100 dB. The alarm still triggers within 1 second of detection.
What is the difference between in general and in no case less than?
The sample says danger zones are in general not less than 2 m, 7 m and 3 m. Some contract specifications say in no case less than, which makes them hard minimums. Kodifly sets them as minimums in both.
Does Kodifly meet both versions?
Yes. Kodifly delivers the components, quantities, alarm levels and data duties each version sets, and returns a filled compliance matrix with the tender.
Related guides
More Smart Site Safety guides
- 4S and DWSSHow the 4S centralised management platform joins the DWSS Smart Construction Management hub under DEVB TC(W) Nos. 3/2023 and 8/2025, and what flows into it.
- AI cameraDEVB TC(W) No. 3/2023 clause 5(12)(g): the unsafe scenarios an AI camera must detect, the 80% test and 90% average accuracy, 1 second alarms and video records.
- Centralised platformWhat DEVB TC(W) No. 3/2023 requires of the 4S centralised management platform (CMP): 30 users, 3 months of data, security, and the alerts every device sends it.
- 4S componentsThe twelve 4S components in DEVB TC(W) No. 3/2023 Annex A, what each must do, and the rules that apply to every device. Kodifly delivers the set complete.
- Confined spaceDEVB TC(W) No. 3/2023 clause 5(12)(h): worker counting, PPE checks and oxygen, gas and temperature monitoring for confined spaces under Cap. 59AE.
- API and dataHow a 4S platform shares and protects data: API access, OpenAPI v3, single sign-on, SFTP data hub, DWSS links, Tier 3 hosting and data return at the end of the contract.
- 4S Labelling SchemeHow the CIC and DEVB 4S Labelling Scheme works: who applies, what CIC assesses, the site inspection, one-year validity, renewal and confiscation.
- Mobile plant alertDEVB TC(W) No. 3/2023 clause 5(12)(e): 360 degree sensors on excavators and cranes, a 2 m danger zone, 100 dB siren, and the BD mandatory rules for private works.
- Permit-to-workWhat DEVB TC(W) No. 3/2023 clause 5(12)(c) requires of a digitised permit-to-work system: the high-risk activities, live mobile status and expiry alerts.
- Plant and tool trackingDEVB TC(W) No. 3/2023 clause 5(12)(b): a unique digital ID on every plant, MEWP, lifting gear and powered tool, with scan checks and overdue alerts.
- Smart lockDEVB TC(W) No. 3/2023 clause 5(12)(d): electronic locks and keys on electrical cabinets, floor openings, lift shafts and confined spaces, with siren and alerts.
- Tower crane alertDEVB TC(W) No. 3/2023 clause 5(12)(e): the tower crane loading and unloading danger zone of at least 7 m from the hook, 3 m clearance, 100 dB siren and alerts.
- VR safety trainingDEVB TC(W) No. 3/2023 clause 6: half-yearly VR safety training for workers in eight high-risk activities, accepted content, hardware and training records.
- Worker monitoringDEVB TC(W) No. 3/2023 clause 5(12)(f): wearables for every worker with location, standstill, temperature and heart rate alerts, and privacy limits.
Send us your 4S compliance matrix
Send the particular specification and the matrix from your tender. We will return each line with the clause and how SpatialSense meets it.