Subpart J
Only employees who are thoroughly trained in the employer's sewer entry procedures and who demonstrate they follow those procedures exactly should be designated as entrants. See OSHA's Sewer System Entry guidance in 1910.146 App E, which emphasizes that sewer entrants are usually experienced and must adhere strictly to employer procedures before and during each entry.
Monitoring equipment should sound an audible alarm when the atmosphere meets any of these conditions: oxygen concentration less than 19.5%; flammable gas or vapor at 10% or more of the lower flammable limit (LFL); hydrogen sulfide at or above 10 ppm (8‑hour TWA); or carbon monoxide at or above 35 ppm (8‑hour TWA). OSHA's Sewer System Entry guidance in 1910.146 App E lists these alarm set points and recommends audible alarms in addition to visual readouts.
Use broad-range (oxygen/broad-range hydrocarbon) sensors for initial or unknown-contaminant situations and use substance-specific sensors when you know the likely contaminants and need exact concentrations for protection decisions. OSHA's Sewer System Entry guidance in 1910.146 App E explains that broad-range sensors give an overall class-level warning while substance-specific instruments measure actual levels of particular hazards and are vital when you must set ventilation or PPE requirements.
Atmospheric monitoring equipment must be calibrated according to the manufacturer's instructions. OSHA's Sewer System Entry guidance in 1910.146 App E requires calibration per the maker's directions so the device reliably alarms at the thresholds cited for oxygen, flammables, hydrogen sulfide and carbon monoxide.
Yes; when several entrants work together in the same immediate location, one instrument used by the lead entrant is acceptable. OSHA's Sewer System Entry guidance in 1910.146 App E states the selected testing instrument should be carried and used by the entrant (or lead entrant) to monitor the entrant's environment and movement direction.
Employers must recognize that sensors may not detect every potentially lethal contaminant and that sewer atmospheres can suddenly change; thus monitoring is necessary but not foolproof. OSHA's Sewer System Entry guidance in 1910.146 App E explains this limitation and states employers must select instruments based on knowledge of their sewer system and be prepared for unpredictable atmospheric changes. For oxygen-deficient hazards specifically, see OSHA's interpretation on oxygen-deficient atmospheres in HVAC which reinforces that oxygen concentrations below 19.5% are hazardous and require appropriate respiratory protection and precautions.
Employers should use measurements from substance-specific devices to make protection decisions—such as required ventilation rates or selection of respiratory protection—because those devices give actual contaminant concentrations. OSHA's Sewer System Entry guidance in 1910.146 App E stresses that substance-specific readings are vital when setting and attaining appropriate entry conditions and choosing controls like ventilation or PPE.
Sewer crews should establish and maintain liaison with the local weather bureau and fire and emergency services so work can be delayed or entrants withdrawn whenever lines might flood from rain, firefighting activities, or emergency releases. OSHA's Sewer System Entry guidance in 1910.146 App E specifically recommends this coordination to reduce the risk of sudden surge flows and flooding during sewer entries.
Large-bore sewer entries may require special equipment such as atmosphere monitors with automatic audible alarms, escape self-contained breathing apparatus (ESCBA) with at least a 10‑minute air supply (or other NIOSH‑approved self‑rescuer), waterproof flashlights, boats or rafts, radios, and rope stand-offs for negotiating bends. OSHA's Sewer System Entry guidance in 1910.146 App E lists these items and stresses selecting equipment appropriate to the sewer conditions.
An oxygen-deficient atmosphere (oxygen below 19.5%) must be treated as immediately dangerous to life or health (IDLH), and appropriate respiratory protection procedures must be used. OSHA's Sewer System Entry guidance in 1910.146 App E sets the 19.5% oxygen alarm point, and OSHA's interpretation on oxygen-deficient atmospheres in HVAC explains that oxygen‑deficient atmospheres fall under respiratory protection requirements and should be treated as IDLH hazards when appropriate.
Only the employer can decide which testing instrument is best for a specific entry operation based on the employer's knowledge and experience with the sewer permit spaces in the workplace. OSHA's Sewer System Entry guidance in 1910.146 App E states employers must consider unique circumstances—including the predictability of the atmosphere—when selecting monitoring equipment.
Entrants should be trained in the use of atmospheric monitoring equipment, including recognizing audible and visual alarms, proper carrying and use while advancing, and following instrument calibration and maintenance procedures. OSHA's Sewer System Entry guidance in 1910.146 App E requires entrants to be trained and equipped with monitors that sound audible alarms at specified thresholds.
If likely contaminants are identified, employers should use substance-specific devices to measure concentrations for setting controls, but broad-range sensors still have value for detecting unexpected classes of hazards. OSHA's Sewer System Entry guidance in 1910.146 App E explains that broad-range sensors are best for initial unknown situations while substance-specific instruments are better when contaminants are known and employer decisions depend on precise levels.
No; the unpredictability of sewer atmospheres does not excuse employers from designing and implementing appropriate permit-space controls—rather, it requires employers to consider unique sewer hazards and may necessitate more conservative controls (continuous monitoring, ESCBA, liaison with emergency services). OSHA's Sewer System Entry guidance in 1910.146 App E highlights that sewers often cannot be fully isolated and can change suddenly, so employers must plan accordingly and use appropriate protective measures.