What are considered pyrotechnic VDS?

Pyrotechnic Visual Distress Signals (VDS) refer specifically to devices that produce visible signals through combustion, such as flares. These signals are used to alert others to a vessel in distress, often producing a bright flame or burst of light that can be seen over long distances and in varying weather conditions. The presence of smoke and flames associated with these signals helps in attracting attention and ensures that rescue operations can locate the distressed vessel quickly.

Other options either describe signals that do not produce flames or smoke, or that might not meet the pyrotechnic criteria. For instance, non-combustible signals do not generate the heat or illumination characteristics of pyrotechnic devices. Visual distress without fire could encompass various signaling methods that do not include the combustion element, thus excluding pyrotechnics. Manually activated signals could refer to several signal types, not exclusively limited to pyrotechnic devices, and may encompass mechanical or reflective types as well. Therefore, smoke and flames are definitive characteristics that classify a signal as pyrotechnic, making this the correct choice.