What must be done to a combustion appliance if carbon monoxide levels exceed 300 ppm?

When carbon monoxide levels exceed 300 ppm, it indicates a dangerous situation that poses serious health risks. The requirement to service the unit is essential to address any potential malfunctions or issues that may be contributing to the elevated carbon monoxide levels. Servicing the appliance could include cleaning, adjusting, repairing, or even replacing components that are not functioning properly. This ensures that the combustion appliance operates safely and efficiently, reducing the risk of harmful emissions.

Additionally, it is vital to ensure that the appliance is safe for continued use, as excessive carbon monoxide can lead to serious health consequences. Therefore, taking the necessary steps to service the unit is critical for the safety of the occupants and the integrity of the appliance itself. Ignoring the situation or simply retesting without action would not resolve the underlying issue, while outright replacement may not be necessary if the unit can be effectively serviced.