AHA Updated CHFM Exam Questions and Answers by chaya

22% excess oxygen is far higher than normal (typical excess O₂ is 3–6%). This means there is too much air compared to fuel, causing inefficiency.

The corrective action is to increase fuel pressure, which reduces excess oxygen by balancing the air-fuel ratio.

D. Increase the fuel pressure (Correct): Restores optimal combustion balance.

A. Steam atomization: Not relevant unless using certain oil burners.

B. Increase nozzle air pressure: Would worsen the excess O₂ condition.

C. No adjustment necessary: Incorrect because efficiency is compromised.

NFPA 25 (2011), Standard for the Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems, specifies that a fire pump flow test must be performed annually. This ensures that the pump delivers adequate flow and pressure under actual operating conditions. Weekly no-flow (churn) tests are also required, but full-flow condition testing is mandated at least once per year.

A low-water cut-off is a safety device that shuts down the burner when water level falls below a safe operating point. This prevents catastrophic overheating and potential boiler explosion. It does not stop steam flow, air supply, or water feed; instead, it directly interrupts burner operation.

NFPA 72, National Fire Alarm and Signaling Code, is the controlling standard for inspection, testing, and maintenance (ITM) of fire alarm and signaling systems (see the ITM chapter—commonly Chapter 14). It details testing frequencies, procedures, and documentation requirements for initiating devices, notification appliances, control equipment, and interfaces.