An automated storage and retrieval system comprising a fire extinguisher assembly (2,3) for extinguishing fire on and within the automated storage and retrieval system, wherein the automated storage and retrieval system further comprises - a rail system comprising - a first set of parallel rails arranged in a horizontal plane and extending in a first direction, and - a second set of parallel rails arranged in the horizontal plane and extending in a second direction which is orthogonal to the first direction; which first and second sets of rails (110,111) form a grid pattern in the horizontal plane comprising a plurality of adjacent grid cells of length L gc and width W gc, each comprising a grid opening defined by a pair of adjacent rails of the first set of rails and a pair of adjacent rails of the second set of rails; - a plurality of stacks of storage containers arranged in storage columns located beneath the rail system; and - a plurality of container handling vehicles (200,300) for lifting and moving storage containers stacked in the stacks, the container handling vehicles (200,300) being configured to move laterally on the rail system above the storage columns to access the storage containers via the grid openings, wherein the fire extinguisher assembly (2,3) comprises - a service vehicle comprising propulsionmeans (6,7) allowing movement of the service vehicle and a fire extinguisher compartment for containing firefighting equipment; and - the firefighting equipment contained in the fire extinguisher compartment, for extinguishing fire on and beneath the rail system using fire extinguishant, characterized in that the propulsion means (6,7) allows movement of the service vehicle across the rail system and comprises a caterpillar track (6,7) configured to drive on top of the rail system, wherein the caterpillar track (6,7) has a length L pm at the level of the horizontal plane exceeding a length corresponding to a diagonal length across a maximum grid opening of the rail system when the service vehicle is moving across the rail system. - a rail system comprising - a first set of parallel rails arranged in a horizontal plane and extending in a first direction, and - a second set of parallel rails arranged in the horizontal plane and extending in a second direction which is orthogonal to the first direction; which first and second sets of rails (110,111) form a grid pattern in the horizontal plane comprising a plurality of adjacent grid cells of length L gc and width W gc, each comprising a grid opening defined by a pair of adjacent rails of the first set of rails and a pair of adjacent rails of the second set of rails; - a first set of parallel rails arranged in a horizontal plane and extending in a first direction, and - a second set of parallel rails arranged in the horizontal plane and extending in a second direction which is orthogonal to the first direction; which first and second sets of rails (110,111) form a grid pattern in the horizontal plane comprising a plurality of adjacent grid cells of length L gc and width W gc, each comprising a grid opening defined by a pair of adjacent rails of the first set of rails and a pair of adjacent rails of the second set of rails; - a plurality of stacks of storage containers arranged in storage columns located beneath the rail system; and - a plurality of container handling vehicles (200,300) for lifting and moving storage containers stacked in the stacks, the container handling vehicles (200,300) being configured to move laterally on the rail system above the storage columns to access the storage containers via the grid openings, - a service vehicle comprising propulsionmeans (6,7) allowing movement of the service vehicle and a fire extinguisher compartment for containing firefighting equipment; and - the firefighting equipment contained in the fire extinguisher compartment, for extinguishing fire on and beneath the rail system using fire extinguishant,