Displayed massege to check air flow

With most projectors there is a foam air filter behind a grill that is the opening to the cooling channels. A fan ensures air flow to cool the lamp, etc. This filter prevents dust from gumming up the works (and depending on design) may prevent dust getting into the optics. As the filter gets dirty it gradually cuts off the air and at some point a protective circuit kicks in and turns off the lamp.
If the projector is on you will feel a stream of hot air coming out of the exit vent. Projectors vary in terms of amount of air flow, so its difficult to define what is normal for a specific model. However, you can simply hold a hand in front of the vent and see if there is air flow (It will be hot air so, careful). If there is a "good" stream of air things are fine, but if only a very light flow is felt the filter may be dirty.
If the filter has not been cleaned or replaced recently make sure the projector is turned off and cooled down then take off the inlet cover and remove the filter. Clean or replace per the instructions for the projector (and periodically as defined .. but taking into account the operating conditions). Once cleaned turn on the projector and feel the "normal" air current for future reference.
Heat is one of the major causes of projector failure, so make sure cooling vents (inlet and outlet) are not obstructed and filters are kept clean