Sodium metal is flammable and exothermically generates hydrogen gas which can spontaneously light on fire in the presence of acids and water.  Larger blocks of sodium metal, however, only slowly react and form a layer of inert oxides and hydroxides on the surface which render the outer surface largely inert from atmospheric moisture. 

Sodium metal can safely be handled with gloves for short periods of time out in the open without fear of fire.  Finely powdered sodium metal should never be handled in the open as exposure to moisture will both reduce the quality of the reagent as well as potentially cause large fires which are difficult to extinguish.

If there is a fire, DO NOT attempt to extinguish it with water.  DO NOT attempt to extinguish it with a normal fire extinguisher - as this will propagate the flaming material across the room by blasting it with pressurized carbon dioxide.  To extinguish a metal fire, it is ideal to either use an appropriate Metal "Class D" fire extinguisher or to pour large quantities of SAND over the fire.

Sodium Metal can be quenched by addition of organic protic solvents, usually highly branched ones such as tert-butanol are used as they react slowest.  Avoid quenching with water as this may result in an explosive fire.