A method to check a roasting system , said system comprising : - at least one roasting apparatus , said apparatus producing smoke during the heating of coffee beans, and - at least one smoke treating unit configured to treat at least a part of the flow of smoke produced by the at least one roasting apparatus, said smoke treating unit comprising at least one removable filtering device , - a smoke driver configured to drive smoke from the roasting apparatus to said at least one filtering device, wherein the at least one smoke treating unit comprises at least one couple of a first and a second temperature sensors, the first temperature sensor being configured to measure the temperature T 1 of the flow of smoke upstream said at least one removable filtering device and the second temperature sensor configured to measure the temperature T 2 of the flow of smoke downstream said at least one removable filtering device, wherein the method comprises the steps of: - operating the roasting apparatus in order to produce hot gas, - monitoring the first and the second temperatures measured by one of the couples of a first and a second temperature sensors during at least a period of time of said operation, - observing the difference of behaviours of the monitored temperatures along time, - comparing said observed difference of behaviours to a predetermined difference of behaviours corresponding to the presence of said at least one removable filtering device between the two temperature sensors, - if the observed difference of behaviours diverges from the predetermined difference of behaviours, then displaying an alarm. - at least one roasting apparatus , said apparatus producing smoke during the heating of coffee beans, and - at least one smoke treating unit configured to treat at least a part of the flow of smoke produced by the at least one roasting apparatus, said smoke treating unit comprising at least one removable filtering device , - a smoke driver configured to drive smoke from the roasting apparatus to said at least one filtering device, wherein the at least one smoke treating unit comprises at least one couple of a first and a second temperature sensors, the first temperature sensor being configured to measure the temperature T 1 of the flow of smoke upstream said at least one removable filtering device and the second temperature sensor configured to measure the temperature T 2 of the flow of smoke downstream said at least one removable filtering device, wherein the method comprises the steps of: - operating the roasting apparatus in order to produce hot gas, - monitoring the first and the second temperatures measured by one of the couples of a first and a second temperature sensors during at least a period of time of said operation, - observing the difference of behaviours of the monitored temperatures along time, - comparing said observed difference of behaviours to a predetermined difference of behaviours corresponding to the presence of said at least one removable filtering device between the two temperature sensors, - if the observed difference of behaviours diverges from the predetermined difference of behaviours, then displaying an alarm. - operating the roasting apparatus in order to produce hot gas, - monitoring the first and the second temperatures measured by one of the couples of a first and a second temperature sensors during at least a period of time of said operation, - observing the difference of behaviours of the monitored temperatures along time, - comparing said observed difference of behaviours to a predetermined difference of behaviours corresponding to the presence of said at least one removable filtering device between the two temperature sensors, - if the observed difference of behaviours diverges from the predetermined difference of behaviours, then displaying an alarm. <EOS>