Safe entry into sanitary sewers requires strict precautions. Which of the following statements is clearly incorrect and unsafe with respect to permitting workers to enter a sewer?

Introduction / Context:
Confined space entry into sewers is hazardous due to toxic gases (H₂S), oxygen deficiency, and explosion risks (methane). Occupational safety protocols mandate ventilation, testing, and emergency preparedness.

Given Data / Assumptions:

• Entry into an active or recently active sanitary sewer.
• Presence of potential toxic and flammable atmospheres.
• Standard confined-space procedures apply.

Concept / Approach:
Safe practice includes ventilation (opening manholes and forced air if needed), pre-entry atmospheric testing, continuous monitoring, proper PPE, and rescue readiness. Any practice that introduces ignition sources (e.g., smoking) is strictly prohibited because sewer atmospheres may contain methane and volatile organics.

Step-by-Step Solution:
List accepted precautions: ventilation, gas testing, barricading, trained personnel, rescue gear.Identify the statement that advocates an ignition source (smoking) in a potentially explosive atmosphere.Conclude it is incorrect and unsafe.

Verification / Alternative check:
Standard safety codes (confined space entry) forbid open flames and smoking; calibration-checked gas detectors are used to test oxygen, H₂S, CO, and combustible gases instead.

Why Other Options Are Wrong:

• Ventilating manholes: Correct and necessary.
• Gas testing: Mandatory.
• Warning signs/barricades: Required for site safety.
• Rescue/ventilation equipment: Essential preparedness.

Common Pitfalls:
Relying on smell to detect H₂S (olfactory fatigue); entering without retrieval lines; neglecting continuous monitoring during work.

Final Answer:
Workers should be advised to smoke in the sewer to check for gas presence