Which choice reflects a situation where a luminous device cannot be installed?

The establishment of restrictions on the installation of luminous devices often revolves around safety considerations and the potential hazards associated with their proximity to certain conditions. A luminous device, particularly when used in lighting applications, may be adversely affected by high temperatures or environmental hazards that can arise from being too close to an open flame.

In the case of an installation near an open flame, the heat produced could damage the luminous device, leading to malfunction or even a fire hazard. Additionally, sources of ignition from an open flame could increase the risk of combustible materials igniting if they are placed too closely, thereby creating a dangerous situation.

In contrast, situations such as being in a properly ventilated area, on a secure mounting surface, or in a well-lit environment don't inherently pose these safety risks. Proper ventilation ensures heat dissipation, a secure mounting surface provides stability, and a well-lit environment relates more to the effectiveness of illumination rather than safety concerns. Hence, the presence of an open flame is specifically the condition which precludes the safe installation of a luminous device.