Refrigeration (C-38) · Lesson 2 of 8

Machinery Room Triggers and Emergency Exhaust (CMC 1106)

"Machinery Room Triggers and Emergency Exhaust (CMC 1106)" is lesson 2 of 8 in the Refrigeration (C-38) Learning Hub. It opens with "When a Machinery Room Is Required" and works through 6 short steps, then a worked example you can check yourself against.

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Steps in this lesson

  1. When a Machinery Room Is Required
  2. Emergency Exhaust: Q = 100 x the Square Root of G
  3. Where the Exhaust Inlet and Makeup Air Go
  4. Detectors, Alarms and the Emergency Shutoff
  5. Doors, Walls and Access
  6. Fire Code Thresholds That Ride Along

The worked example in the course applies this lesson to a realistic job in 7 steps, from "Classify the refrigerants" through "Place the equipment".

What you'll be able to do

  • Explain the main idea of "Machinery Room Triggers and Emergency Exhaust (CMC 1106)" in plain language you can use on the exam.
  • Apply this step with confidence: "Where the Exhaust Inlet and Makeup Air Go".
  • Apply this step with confidence: "Detectors, Alarms and the Emergency Shutoff".
  • Apply this step with confidence: "Doors, Walls and Access".
  • Apply this step with confidence: "Fire Code Thresholds That Ride Along".
  • Test yourself on the worked example and the quick-check quiz inside the classroom.
Machinery Room: Trigger and Emergency ExhaustSUPERMARKET MACHINERY ROOMMakeup air inSYSTEM A625 lbR-404ASYSTEM B400 lbR-134aDetectorE-stopExhaust inlet within 1 ft of floor (heavier than air)or within 1 ft of ceiling (lighter than air)Room kept at 104 F or less (1106.7)EMERGENCY EXHAUST (1106.2.9.1)Q = 100 x √GQ in cfm; G = lb in the largest systemSystem A: 625 lb R-404AQ = 100 x √625 = 100 x 25 = 2,500 cfmSystem B: 400 lb R-134aQ = 100 x √400 = 100 x 20 = 2,000 cfmHighest governs: 2,500 cfmDetector set point: not more than OELR-404A and R-134a OEL = 1,000 ppmMachinery room required: A1 system, 120 hp (1106.1.3)Emergency exhaust not less than 2,500 cfm; alarm at 1,000 ppm or lessALSO REQUIREDVisual and audible alarms inside and outside each door; manual reset inside; 30 s responseBreak-glass shutoff outside the door (1108.3); outward-opening self-closing doors (1106.2.2)Source: 2025 California Mechanical Code 1106.1 - 1106.9, 1108.3; 2025 California Fire Code 608.9.1CC
The diagram for this lesson, exactly as it appears in the Learning Hub.

The first steps of this lesson

Step 1: When a Machinery Room Is Required

2025 CMC Section 1106.1 requires a refrigeration machinery room when any one of these exists: the quantity in a single independent circuit exceeds the amounts of Table 1102.3 (Section 1106.1.1); direct- or indirect-fired absorption equipment is used (1106.1.2); an A1 system has an aggregate combined compressor horsepower of 100 or more (1106.1.3); or the system contains other than a Group A1 refrigerant (1106.1.4). Equipment located outdoors is allowed under ASHRAE 15 as the Exception to Section 1106.1 says, so a rooftop or yard rack is a different path.

Step 2: Emergency Exhaust: Q = 100 x the Square Root of G

Section 1106.2.9 requires an emergency ventilation system able to exhaust a leak or rupture. For A1, A2, A3, B1, B2 and B3 refrigerants, Equation 1106.2.9.1 gives Q = 100 x the square root of G, where Q is airflow in cfm and G is the pounds of refrigerant in the largest system. Where several refrigerants are present, the highest airflow quantity applies. Group A2L and B2L rooms use the separate method in Section 1106.11.11.

The remaining 4 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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