The Naylor 'Spiralarm' type RL-4 flame safety lamp was made in 1956. It was designed primarily as an effective detector of firedamp and dangerous gases.
The 'Spiralarm' used an electrical ignition system, which allowed the lamp to be lit safely underground. The lamp also used an internal flame height gauge to detect when firedamp was present in the atmosphere.
The flame safety lamp was successful in improving the safety of mineworkers in the potentially dangerous atmosphere that existed underground. Flame safety lamps, although remaining in use as gas detectors, began to be replaced by safer and brighter electric lamps at the beginning of the 20th century.