 Advanced Life Support (ALS) resources are sent to all calls - there may be a tiered response with a local fire department providing BLS first response via an engine or truck company, but the level of transporting care is always ALS and always at the paramedic level.Purists will argue, with merit, that a true PUM must encompass all five of these hallmarks.However, many existing PUM operations are a hybrid of a simple third-service EMS organization utilizing one or more of the above listed characteristics in an effort to provide the best advanced life support patient care possible.