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4111, Appendix A: How National Estimates Statistics Are Calculated Estimates are made using the National Fire Incident Reporting System (NFIRS)of the Federal Emergency Management Agency's(FEMA's)United States Fire Administration(USFA), supplemented by the annual stratified random-sample survey of fire experience conducted by the National Fire Protection Association(NFPA),which is used for calibration. Data Bases Used NFIRS provides annual computerized data bases of fire incidents,with data classified according to a standard format based on the NFPA 901 Standard. Roughly three-fourths of all states have NFIRS coordinators,who receive fire incident data from participating fire departments and combine the data into a state data base. These data are then transmitted to FEMA/USFA. Participation by the states,and by local fire departments within participating states, is voluntary. NFIRS captures roughly one-third to one-half of all U.S. fires each year. More than one-third of all U.S.fire departments are listed as participants in NFIRS, although rot all of these departments provide data every year. The strength of NFIRS is that it provides the most detailed incident information of any national data base not limited to large fires. NFIRS is the only data base capable of addressing national patterrs for fires of all sizes by specific property use and specific fire cause. (The NFPA survey separates fewer than 20 of the hundreds of property use categories defined by NFPA 901 and solicits no cause-related information except for incendiary and suspicious fires.) NFIRS also captures information on the avenues and extent of flame spread and smoke spread and on the performance of detectors and sprinklers. 41111 The NFPA survey is based on a stratified random sample of roughly 3,000 U.S.fire departments(or just over one of every ten fire departments in the country). The survey includes the following information: (1)the total number of fire incidents, civilian deaths,and civilian injuries,and the total estimated property damage(in dollars),for each of the major property use classes defined by the NFPA 901 Standard;(2)the number of on-duty firefighter injuries,by type of duty and nature of illness; and(3)information on the type of community protected(e.g., county versus township versus city)and the size of the population protected,which is used in the statistical formula for projecting national totals from sample results. The NFPA survey begins with the NFPA Fire Service Inventory, a computerized file of about 30,000 U.S. fire departments,which is the most complete and thoroughly validated such listing in existence. The survey is stratified by size of population protected to reduce the uncertainty of the final estimate. Small rural communities protect fewer people per department and are less likely to respond to the survey, so a large number must be surveyed to obtain an adequate sample of those departments. (NFPA also makes follow-up calls to a sample of the smaller fire departments that do not respond,to confirm that those that did respond are truly representative of fire departments their size.) On the other hand,large city departments are so few in number and protect such a large proportion of the total U.S. population that it makes sense to survey all of them. Most respond, resulting in excellent precision for their part of the final estimate. Projecting NFIRS to National Estimates To project NFIRS results to national estimates,one needs at least an estimate of the NFIRS fires as a fraction of the total so that the fraction can be inverted and used as a multiplier