IS 11972:1987 is the Indian Standard (BIS) for safety precautions to be taken when entering a sewerage system. This code of practice details the essential safety precautions for personnel entering sewerage systems and other similar confined spaces. It covers atmospheric testing for hazardous gases, forced ventilation requirements, mandatory personal protective equipment (PPE), and procedures for emergency rescue to prevent accidents.
Code of practice for safety precautions to be taken when entering a sewerage system
| Parameter | IS Value | International | Source |
|---|---|---|---|
| Acceptable Oxygen Level for Entry | Should be above 19% by volume. | Between 19.5% and 23.5% by volume. | OSHA 29 CFR 1910.146 |
| Flammable Gas/Vapor Concentration | Not explicitly defined in % LEL; presence must be tested for. De facto industry practice is <10% LEL. | Less than 10% of the Lower Explosive Limit (LEL). | OSHA 29 CFR 1910.146 |
| Hydrogen Sulfide (H2S) Limit | Not specified in the code. Value of 10 ppm (TWA) is taken from the Indian Factories Act. | 10 ppm (Permissible Exposure Limit for entry). | OSHA 29 CFR 1910.146 |
| Carbon Monoxide (CO) Limit | Not specified in the code. Value of 50 ppm (TWA) is taken from the Indian Factories Act. | 35 ppm (often used as the action level, based on NIOSH REL). | CSA Z117.1 / NIOSH Guidance |
| Definition of Roles | Mentions 'supervisory staff', 'workmen', and a 'standby man'. | Formally defines 'Authorized Entrant', 'Attendant', and 'Entry Supervisor' with specific duties. | OSHA 29 CFR 1910.146 |
| Training Recurrence | Training is required, but no specific recurrence interval is mentioned. | Retraining is required when job duties change, there are program changes, or performance is deficient (performance-based). | OSHA 29 CFR 1910.146 |