"Over the decade, a significant amount of study has focused on scientifically evaluating the much-discussed NFPA [National Fire Protection Association] 1710 fire scene staffing recommendations, most recently and principally by the National Institute of Standards and Technology (NIST). Little research however, has been conducted regarding the EMS [emergency medical services] scene staffing recommendations also contained in NFPA 1710. In 2010, NIST published the Report on EMS Field Experiments, specifically addressing the NFPA 1710 EMS scene staffing suggestion of two advanced level providers and two basic level providers on every EMS scene. Though the study examined skill-level distribution on EMS scenes, it did not examine the actual need for a second paramedic."
United States Fire Administration: http://www.usfa.fema.gov/