Which of the following conditions can trigger a residential carbon monoxide detector?

The correct choice indicates that a residential carbon monoxide detector can be triggered by very high concentrations of carbon monoxide (CO) in a short period. This is due to the nature of how CO detectors are designed to function; they are calibrated to sense elevated levels of CO quickly because this gas is not only highly toxic but can also be life-threatening in a short timeframe.

Carbon monoxide is produced by the incomplete combustion of fossil fuels, and exposure to high concentrations poses immediate health risks. Detectors monitor the concentration of CO in the air and, when it reaches a certain threshold within a specific time frame, the alarm will activate, alerting residents to the potentially dangerous situation.

In contrast, while very low concentrations of CO over a long duration could eventually pose a risk, it typically does not trigger the alarm as quickly as high levels would. Prolonged exposure to natural gas does not directly activate a carbon monoxide detector because the detection is specific to carbon monoxide, not natural gas itself. Lastly, smoke from a fire, although indicative of a hazardous situation, does not affect CO detectors directly unless it is accompanied by the production of CO. Therefore, the most accurate condition that would trigger the detector is indeed the presence of very high concentrations of carbon monoxide in a short period