The butane for refillable lighters uses compressed air to force the butane from the can into the lighter. During the filling process, air becomes trapped in the lighter. Before refilling the butane lighter, it is necessary to purge the air from the lighter. This helps to tell when a butane lighter is filled. The key to filling the butane lighter to capacity is to continue filling until the compressed air escapes from the lighter.
Hold the butane lighter upside down and angle the fill hole away from your face. Turn the flame adjustment wheel to its lowest setting. Some lighters have a screw that require a small flat-head screwdriver to adjust the flame height.
Press the center of the butane fill hole with the small flat-head screwdriver to allow air to release from the lighter.
Shake the butane refill canister vigorously and place the tip of the can nozzle over the refill hole. Press the can and nozzle down to begin filling the butane lighter.
Release the can from the lighter once air begins to pass through the seal between the nozzle and the refill hole. There is a seal around the center of the refill hole that allows air to expel once the lighter is full. The butane lighter is now full.