From 1 January 2025, it will be mandatory in the UK for a functioning carbon monoxide (CO) detector capable of alerting via aural and/or visual warnings to be fitted in certain piston-engine aircraft when operating with passengers. The aim is to restore "an acceptable level of safety".  CO poisoning has been cited as a factor in multiple general aviation accidents globally. Under CAA Safety Directive SD-2024/001 (V2), which comes into effect from 1 January 2025, the Civil Aviation Authority (CAA) will recognise both aviation-standard and commercial, off-the-shelf CO detectors. As to the latter, there is a wide range of competitively priced, commercially available units intended for use in domestic environments. Although not specifically approved for aviation use, findings from the CAA’s 12-month study suggest that these devices can function reasonably at typical recreational GA altitudes.