Abstract
Abstract
Sewer gas intrusion arising from noncompliant plumbing is an underexamined indoor-air hazard with implications for building safety and occupational exposure. This study evaluates a plausible chronic inhalation scenario for long-term hotel staff and documents the plumbing failures that created it, using two independently renovated hotels in China as field-verified case studies. Direct inspection confirmed absent or defective water traps and unsealed toilet-to-drainpipe connections at both sites. Indoor hydrogen sulfide H
2
S concentrations were measured with a calibrated electrochemical sensor and ranged from 0.0044 to 0.0159 mg/m
3
at steady state, with a 45-second post-flush peak of 0.0266 mg/m
3
. A single-compartment mass-balance model, parameterized with literature-derived emission and ventilation ranges and validated against field measurements, produced a central hazard quotient (HQ) of approximately 1.2 for hotel staff (8 h/day, 250–350 d/year). A Monte Carlo simulation yielded a median HQ of 0.6 and a 95th-percentile value of 2.2, with roughly 1/4 of plausible parameter combinations exceeding HQ = 1. The measured post-flush peak remained below the Agency for Toxic Substances and Disease Registry acute-duration benchmark. Sewer gas intrusion from noncompliant plumbing can generate chronic exposures at or modestly above regulatory thresholds, underscoring the need for mandatory post-installation inspections and improved plumbing code enforcement.