Light sources

Light sources are used by players via the Firemaking skill, in order to illuminate their way through dark caves and dungeons. Without them, some dungeons are pitch black and visibility is zero. The access to some dungeons is prohibited without a light source in hand. If a player attempts to extinguish a light source in an area where they need it (with the "extinguish" option), the game will not let them.

Consequences
The absence of a light source while in a dark area triggers the following message: You hear tiny insects skittering over the ground...

A few seconds later, another message appears, which says: Tiny biting insects swarm all over you!

The player will then start to get multiple hits of 10 life points or below very quickly until he/she dies or relights their lamp. No Magic, item or Protection prayer can negate the damage. However certain Emotes, such as Give Thanks, though unable to block the attacks, can temporarily slow their infliction. Once out of the movement phase of the emotes, you will get hit for the damage that you have missed while in the movements.

Explosion of gas
Oil lamps, candle lanterns, torches and candles can provoke an explosion in the Lumbridge Swamp cave, which extinguishes the lamp and causes up to 160 life points of damage.

Giant Mole
Sometimes, the Giant Mole will retreat by digging through the ground. If you stand near him while he's retreating, the mud from the ground will extinguish your light source.

Dark dungeons
The following locations require light sources:
 * A genie's cave west of Nardah
 * Dorgesh-Kaan South Dungeon
 * Falador Mole Lair
 * Lumbridge Swamp Caves
 * Mos Le'Harmless Caves
 * Skavid Caves
 * Sophanem Dungeon
 * Temple of Ikov, room downstairs

Types of light source
Apart from the bullseye lantern and all versions of the Seer's headbands, light sources can go out. For instance, a candle could be doused by a minor gust of cave wind. Moreover, the exposed flame could provoke an explosion of gas. Therefore one should consider the candle lantern as the worst of the lanterns and should try to acquire an oil version.

Falling into the water also extinguishes the light, if one attempts but fails an Agility shortcut, such as the one in the Lumbridge Swamp Caves. The lens of the bullseye lantern may shatter, and the light may be extinguished, by a fall. If the lens is shattered, the candle cannot be relit, and "tiny insects" will begin to appear.

Light source items all need a tinderbox to be lit, with the exception of torches which can also be lit with dry sticks. Most lit light sources cannot be traded unless they are extinguished.

Members can light lanterns to see in dimly lit underground dungeons. However, certain Firemaking levels are needed to light different kinds of lanterns. No experience is received when lighting a lantern. Some lanterns require glass, which can be made by using the Crafting skill.

There are three levels of brightness (1 being the lowest and 3 the highest) and the brightness does stack to add up to 3. Therefore, three torches are equivalent in light to one bullseye lantern.

Filling sources
One may acquire the empty or the filled version of the oil lamp, oil lantern and bullseye lantern. In order to fill them, one has to distill swamp tar in the chemist's in Rimmington or at the lamp stall in Dorgesh-Kaan.

Shops

 * Torches can be purchased in cities such as Dorgesh-Kaan, Keldagrim, Shilo Village, Tai Bwo Wannai, Yanille, the Grand Exchange and by trading with other players.
 * The Candle Seller standing near the entrance of the Lumbridge Swamp Caves sells candles for 1000 coins.
 * There is a candle shop in Catherby where players may purchase white or black candles, for 1 coin each.
 * Miltog's lamp shop has torches, mining helmets and tinderboxes in its main stock and other light sources in its player stock.
 * Players can steal candles from the north-east table in the Saradomin church on Entrana. Failing deals 30 life points of damage and produces the message "A higher power smites you."

Other kinds of light

 * Despite being a lantern, the bug lantern item cannot be used as a light source. It is used in the Slayer skill giving the ability to kill Harpie Bug Swarms. It requires 33 Slayer to wield.
 * The city of Dorgesh-Kaan is kept alight by hundreds of magical lamps. As these lamps often break, one needs to repair them with the help of light orbs. This is one way to gain some Firemaking experience.

Trivia

 * Although combining multiple level one or two light sources can increase their collective brightness, a total brightness level above 3 makes no difference.
 * Dungeons that require these are the only locations where you are able to adjust the lighting without changing graphics options, making it a possible tool for videomaking.
 * If you find yourself in a dungeon without a light source or a teleport (home teleport does not work when being attacked by bugs), you have a grace period of roughly 10 seconds to get to an area where a light source is not required.