Sanitation System (C-42) · Lesson 6 of 6

Entering a Septic Tank or Sewer: Confined-Space Atmosphere Rules

"Entering a Septic Tank or Sewer: Confined-Space Atmosphere Rules" is lesson 6 of 6 in the Sanitation System (C-42) Learning Hub. It opens with "A Tank Is a Confined Space, Often a Permit Space" and works through 5 short steps, then a worked example you can check yourself against.

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Steps in this lesson

  1. A Tank Is a Confined Space, Often a Permit Space
  2. What Counts as a Hazardous Atmosphere
  3. Test in the Right Order, With a Calibrated Meter
  4. Attendant, Permit, and Rescue
  5. The Excavation Around the Tank

The worked example in the course applies this lesson to a realistic job in 6 steps, from "Flammable gas second" through "What happens next".

What you'll be able to do

  • Explain the main idea of "Entering a Septic Tank or Sewer: Confined-Space Atmosphere Rules" in plain language you can use on the exam.
  • Apply this step with confidence: "Test in the Right Order, With a Calibrated Meter".
  • Apply this step with confidence: "Attendant, Permit, and Rescue".
  • Apply this step with confidence: "The Excavation Around the Tank".
  • Test yourself on the worked example and the quick-check quiz inside the classroom.
Septic Tank Entry: Test Before You Go InENTRY SET-UP (not to scale)retrievaldeviceENTRANTharness + lineATTENDANTstays outside20 in min.opening7 ft deep (over 5 ft): mechanical retrieval deviceREADINGS BEFORE ENTRYTest (in order)ReadingLimit1. Oxygen20.9 %19.5-23.5OK2. Flammable gas4 % LFL10 % LFLOK3. Hydrogen sulfide14 ppm10 ppmALARM3. Carbon monoxide18 ppm25 ppmOKEntry rules, 8 CCR 5157:Attendant outside for the whole entrySigned permit; keep canceled permits 1 yrMechanical retrieval if vertical over 5 ftTest oxygen, then flammable, then toxicEnter only if acceptable conditions are metDO NOT ENTER: hydrogen sulfide 14 ppm is over the 10 ppm limitVentilate with clean forced air, re-test in order, then re-evaluate for entryEntrant in harness with retrieval line; attendant outside the whole entry8 CCR 5157(b), (d)(5)(C), (k)(3)(B), Appendices B and E; 2025 CPC Section H 501.5CC
The diagram for this lesson, exactly as it appears in the Learning Hub.

The first steps of this lesson

Step 1: A Tank Is a Confined Space, Often a Permit Space

Title 8 CCR Section 5157(b) defines a confined space as one large enough to enter and work in, with limited or restricted means of entry or exit (tanks, vessels, vaults, and pits are named), and not designed for continuous occupancy. It becomes a permit-required confined space if it contains or has the potential to contain a hazardous atmosphere, an engulfment hazard, a trapping configuration, or another serious hazard. The employer must evaluate the workplace, post danger signs such as "DANGER -- PERMIT-REQUIRED CONFINED SPACE, DO NOT ENTER," and either keep employees out or write and follow a permit space program (Section 5157(c)).

Step 2: What Counts as a Hazardous Atmosphere

Section 5157(b) lists: flammable gas, vapor, or mist above 10 percent of its lower flammable limit (LFL); oxygen below 19.5 percent or above 23.5 percent; and any substance above its permissible exposure limit. Appendix E (Sewer System Entry) sets the alarm points for sewer entrants at oxygen under 19.5 percent, flammable gas at 10 percent or more of the LFL, and hydrogen sulfide or carbon monoxide at or above their permissible exposure limits (10 ppm or 25 ppm as printed). Do not confuse these with the 20-percent-of-LFL figure used for excavations in Section 1541(g)(1)(C).

The remaining 3 steps, the worked example and the quiz are in the course. This is a preview. The full lesson, with the step-by-step explanations, a worked example and a quick-check quiz, is inside the classroom.

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