In what scenario is lighting a fire indoors deemed unsafe?

Lighting a fire indoors is deemed unsafe when using kerosene without proper ventilation because it can produce harmful gases, including carbon monoxide, which can accumulate in enclosed spaces. Without adequate airflow, the risk of asphyxiation or other health hazards significantly increases. Kerosene burns with a risk of releasing particulates and toxic fumes, making it crucial to ensure that there is sufficient ventilation when using such fuels indoors to maintain safety.

In contrast, natural gas can be safely used indoors as long as appliances are properly installed and vented. Fires conducted in a fireplace are typically considered safe due to the design that allows for proper ventilation and containment of the fire. Electric heaters, when used according to guidelines, do not produce the same risks associated with combustion and are generally safe as well.