Under what condition can an internal combustion engine operate in a confined space?

An internal combustion engine can operate in a confined space only if it is properly ventilated. This is crucial because combustion engines produce exhaust gases, such as carbon monoxide, which can accumulate in confined or poorly ventilated areas, leading to hazardous conditions for operators and anyone nearby. Adequate ventilation ensures that these harmful gases are dispersed, maintaining air quality and reducing the risk of asphyxiation or other health hazards.

While regular maintenance, additional safety features, and the use of alternative fuels can contribute to the overall safety and efficiency of an engine, they do not mitigate the critical need for proper ventilation in confined spaces. Thus, it is the ventilation aspect that directly addresses the safety concern associated with running internal combustion engines in such environments.