Carbon Monoxide Testing
Carbon monoxide testing protocols including instrument calibration, ambient and flue gas measurement points, BPI action levels, documentation requirements, and emergency response procedures.
- Calibrate and verify CO testing instruments before use
- Measure CO at all required ambient and flue gas measurement points
- Apply BPI action levels and determine appropriate response actions
- Document CO testing results per BPI standards
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CO Instruments & Calibration
The Danger of Carbon Monoxide
Carbon monoxide is responsible for more poisoning deaths in the United States than any other single toxic agent. Approximately 430 people die annually from unintentional CO poisoning, with peak incidents during heating season. CO is particularly dangerous because it is colorless, odorless, and tasteless - occupants cannot detect it without instrumentation. Symptoms (headache, dizziness, nausea, confusion) mimic flu or food poisoning, leading to delayed recognition.
CO binds to hemoglobin (the oxygen-carrying molecule in blood) with an affinity approximately 200 times greater than oxygen. Once inhaled, CO prevents blood from carrying oxygen to tissues. Even after removing the person from the CO-contaminated environment, it takes 4-6 hours for the body to eliminate half of the bound CO (at normal atmospheric oxygen levels).
Types of CO Instruments
BPI Heating Professionals use two categories of CO instruments:
Personal CO monitor - A compact, wearable device that continuously monitors ambient CO levels and alarms at preset thresholds (typically 35 ppm and 200 ppm). BPI requires every technician to carry a personal CO monitor whenever entering a building. This instrument protects the technician's own safety.
Combustion analyzer - A more sophisticated instrument that measures CO concentration in flue gas along with O2, CO2, flue temperature, and calculated efficiency. The combustion analyzer is used for appliance-specific testing, not personal protection.
Calibration Requirements
Both instrument types require regular calibration to ensure accurate readings. An uncalibrated CO instrument can read low (missing a dangerous condition) or high (causing unnecessary alarm).
Fresh air zero - Before every use, turn on the instrument in clean outdoor air (away from vehicles, combustion appliances, or other CO sources). Allow the sensor to stabilize and confirm a zero reading. If the instrument does not zero in fresh air, it needs service.
Span calibration - Periodically (per manufacturer's recommendation, typically annually), test the instrument with a known concentration calibration gas (e.g., 100 ppm CO). Verify that the reading is within the manufacturer's accuracy specification (typically +/- 5%).
Sensor replacement - CO sensors have a limited lifespan (typically 2-5 years depending on technology). Replace sensors on the manufacturer's recommended schedule, even if readings appear normal.
Zero in Fresh Air EVERY Time
Always zero your CO instruments in known fresh air outdoors before entering a building. If you zero the instrument inside a building that already has CO present, the instrument will register zero in a contaminated environment. Starting with a known-good zero is the foundation of accurate CO measurement.
CO is the leading cause of poisoning deaths in the US and is undetectable by human senses. BPI requires a personal CO monitor on every building entry and a combustion analyzer for appliance testing. Always zero instruments in fresh outdoor air before entering the building. Sensors have a 2-5 year lifespan and require annual span calibration with known-concentration test gas.