The primus was essentially a portable stove used for cooking.

The primus had a tank that was filled with kerosene. The tank stood on slender legs, and above it was a burner, surrounded by a metal frame on which cooking pots were placed.

Beneath the burner head, there was a U-shaped ring into which alcohol (methylated spirits) was poured and ignited.

A protruding handle on the tank allowed the user to pump and create pressure inside the tank. This pressure caused flames to shoot powerfully from the burner head. As the alcohol burned, the burner head heated up, causing the kerosene that reached it to evaporate.
The kerosene vapors were pushed into the alcohol flame and burned with a blue flame.

Despite the smell and soot from the kerosene, using the primus was still considered cleaner and more efficient than heating with a patilya, which produced much more soot and a stronger kerosene odor compared to the primus.

To turn off the primus, a small key-like handle was rotated, allowing the user to control or extinguish the flame.