A FIREFIGHTER'S EQUIPMENT
1 Helmet and goggles - fitted with protective flaps to cover the face if needed
2 Backpack - contains emergency aluminium shelter, food, water, torch
3 Radio - for communication
4 Protective jacket - made of fire-retardant material, yellow coloured with fluorescent strips for high visibility
5 Axe - to clear trees and vegetation
6 Leather boots - do not have steel toe caps, which attract and retain heat
Modern firefighters tackling forest fires use a range of specialised techniques and equipment.
As well as working under heavy protective clothing in conditions of extreme heat and poor visibility, firefighters must be well-coordinated and work as a team to tackle large fires, which often move quickly and unpredictably.
Firefighters are usually divided into two groups, "hotshots", who fight fires at ground level and "smokejumpers", rapid-response units who parachute into inaccessible areas to tackle small blazes before they intensify and spread.
The basic aim of all firefighting crews is to deny the fire a source of fuel.
Firefighting ranges from high to low technology.
"Hotshot" firefighters on the ground cut down trees and clear scrubland using axes and chainsaws to create a firebreak.
Other firefighters, sometimes using helicopters or aircraft. use thermal-imaging equipment to view the fire through thick smoke.
This enables fire crews to be sent quickly to strategic points ahead of the blaze with the aim of controlling and slowing its path.
A risky technique sometimes used is to start a "backfire" - a controlled blaze to either clear dry woodland and create a break, or with the aim of joining up with the main blaze so the combined fire burns itself out.
The ground-based effort is complemented by airborne tankers and helicopters, which can drop thousands of litres of water or fire-retardant chemicals from low altitude.
Despite their skills and weight of numbers, the difficulty and scale of the firefighters' task are often directed by the random factor of the weather.
The most damaging fires occur in hot, dry and windy conditions - exactly those currently being experienced in California.
Gusty winds can cause large fires to "leap" across fire breaks, undermining the work of the fire crews.
High temperatures and drought prolong the conditions needed by a fire to continuing burning out of control.
Forest fires usually end through a combination of the firefighters' efforts and a change in weather conditions.