A lamp comprises a housing, an inner shell, a fan, a heat sink and a lighting module. The housing has a first compartment and a first opening on an end thereof. The inner shell is adapted to be received in the first compartment and has a second compartment and a second opening on an end thereof, wherein the second opening is aligned with the first opening. An air channel is formed between the housing and the inner shell in the first compartment. The inner shell further comprises a through-hole allowing the first compartment to communicate with the second compartment. The fan is located adjacent to the through-hole and has two air-flowing sides for drawing air in and out of the lamp. The heat sink has a bottom plate with one face facing the fan. The lighting module is adapted to be coupled to another face of the bottom plate.