Every device that you screw into a Campingaz refillable container (901,904,907) including regulators and handles has a synthetic rubber O ring or washer.
The washer is to stop the escape of gas that has managed to get through the screw thread.
Over time the washer may become compressed and crispy. It may begin to leak and the escaping gas catch light from the lamp or cooker flame.
If this happens to you then switch off the cooker or lamp, blow out the flames and unscrew the device from the gas container.
Genuine Campingaz washers do not seem to be available at local camping stockists and on Ebay/Amazon, but a central heating store sold me compatible washers at 30p each.
If you can smell gas you may need a new washer and 30p seems quite reasonable.
A day of all things motorhome and campervan. The show is held both in the main indoor arena and across the grounds. Catering, hot drinks and food options are available. Easy access to the site and free parking included. Win one of five pairs of day tickets