Working in Drainage Services Department Manholes Underground: A Critical Examination of Confined Space Safety Protocols in Hong Kong

In the infrastructure of Hong Kong’s Drainage Services Department (DSD), subterranean manholes provide many occupational hazards, such as toxic and flammable hydrogen sulphide (H₂S), oxygen-deficient environments, explosion risks, trench collapses, and illegal access. The Factories and Industrial Undertakings (Confined Spaces) Regulation mandates training, the designation of “Competent Persons”, and permit-to-work systems; however, the manuscript contends that safety protocols may be qualitative rather than quantifiable, which restricts enforceability and renders decision-making reliant on judgement rather than established thresholds. This essential descriptive audit consolidates observational photographic data and procedural documentation within an international confined-space comparison framework. Research reveals that DSD manhole operations encompass essential control domains—permits, ventilation, personal protective equipment, atmospheric testing instruments, rescue apparatus, shoring, and perimeter control—however, the documented procedures are deficient in quantified atmospheric thresholds, performance benchmarks for ventilation and rescue timing, explicit protocols for communication failures, rationales for standardised inspection frequency, and uniform respiratory protection measures. The study additionally delineates methodological constraints that hinder causal assertions and advocates for a future mixed-method and quantitative monitoring architecture.

confined space, Drainage Services Department

1. American Conference of Governmental Industrial Hygienists (ACGIH). (2026). Guide to Occupational Exposure Values. Cincinnati: ACGIH. [Google Scholar] [Crossref]

2. Ahmed, W., Yusuf, M., & Khan, M. W. (2023). The Silent Threat Below: A Comprehensive Analysis of Manhole Gases and Health Effects. Sprin Journal of Arts, Humanities and Social Sciences, 2(11), 115-126. [Google Scholar] [Crossref]

3. Aventaggiato, L., Colucci, A. P., Strisciullo, G., Favalli, F., & Gagliano-Candela, R. (2020). Lethal Hydrogen Sulfide poisoning in open space: An atypical case of asphyxiation of two workers. Forensic science international, 308, 110122. [Google Scholar] [Crossref]

4. Construction Industry Council (CIC). (2017). Guidance notes on trench safety and shoring inspection (CIC Publication No. 2017-04). [Google Scholar] [Crossref]

5. Doyle, L., McCabe, C., Keogh, B., Brady, A., & McCann, M. (2020). An overview of the qualitative descriptive design within nursing research. Journal of research in nursing, 25(5), 443-455. [Google Scholar] [Crossref]

6. Drainage Services Department (2019). Reporting of Accidents Occurring on Drainage Services Department Works Sites. Drainage Services Department Technical Circular No. 1/2019. [Google Scholar] [Crossref]

7. Health and Safety Executive (HSE), UK. (2014). Confined spaces: A brief guide to working safely (INDG258 rev4). HSE Books. [Google Scholar] [Crossref]

8. Kallepalli, S., Johnson, L., & Mattson, B. (2021). Diffusion of Gases into Air: A Simple Small-Scale Laboratory Activity. Journal of Chemical Education, 98(10), 3258-3262. [Google Scholar] [Crossref]

9. Labour Department. (2024). Code of practice for safety and health at work in confined spaces. Hong Kong: Government Printer. [Google Scholar] [Crossref]

10. Labour Department. (2021). Occupational safety and health statistics 2020–2021. Hong Kong: Government Printer. [Google Scholar] [Crossref]

11. Labour Department. (2025). Occupational safety and health statistics 2024. Hong Kong: Government Printer. [Google Scholar] [Crossref]

12. McEwen, B. J. (2018). Strangulation, suffocation, and asphyxia. In Veterinary Forensic Pathology, Volume 1 (pp. 129-148). Cham: Springer International Publishing. [Google Scholar] [Crossref]

13. McManus, T. N., & Haddad, A. N. (2019). Natural ventilation in isolated subsurface structures in the infrastructure: A review. Environment and Natural Resources Research, 9(2), 61-74. [Google Scholar] [Crossref]

14. National Institute for Occupational Safety and Health (NIOSH). (2016). Criteria for a recommended standard: Occupational exposure to hydrogen sulfide (NIOSH Publication No. 2016-118). [Google Scholar] [Crossref]

15. Occupational Safety and Health Administration (OSHA). (2023). Permit-required confined spaces (29 CFR 1910.146). U.S. Department of Labor. [Google Scholar] [Crossref]

16. Wang, L., Chen, S., & Zhang, Y. (2018). Ventilation efficiency of flexible air ducts in vertical confined spaces. Journal of Occupational Safety and Engineering, 24(3), 215–228. [Google Scholar] [Crossref]

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