Abstract: A method of determining a leak rate of an insulating gas from a gas-insulated compartment of an electrical installation having a plurality of similar compartments, the method being characterized in that it comprises the steps of; periodically determining a gas density for each of the compartments; determining respective straight lines from series of gas densities for each of the compartments; comparing slopes of the determined lines with one another; detecting a leak if the result of a comparison for one of the slopes is greater than a threshold; and in the event of a leak being detected determining a leak rate for the compartment associated with the slope that lead to a leak being detected.