This NFIRSGram explains how to create and define plus-one codes in the National Fire Incident Reporting System (NFIRS).
As a part of data quality checks, the U.S. Fire Administration (USFA) has discovered that 2,922 fire incidents reported in 2014 have duplicate actions taken codes as a result of the use of plus-one codes created by departments.
When departments create a plus-one code, they are further defining the base code, but the base code definition still applies.
If a department creates a plus-one code of 111 with a definition of “Extinguishment by fire service personnel – Using CAFS,” it still means “11 — Extinguishment by fire service personnel.” Thus, the department should not select 11 and 111 as a possible action taken code, as the department has already indicated that it extinguished the fire with its plus-one code.
Likewise, if a department has more than one plus-one code for 11, such as 111, 112, 113, etc., it should not select more than one such code for the incident.
When departments need to create multiple plus-one codes for a single base code, the departments should contact USFA or their state agency for guidance on what they are attempting to collect and the best way of collecting that data.
At the state and national levels, the plus-one code is only defined by the base code. Thus, 111, 112, 114 and 11F all mean 11 at the state and national levels. Using more than one of these codes on the same incident skews the analysis of those incidents. The only time a plus-one code is analyzed at the state or national level is when the state or national group creates a specific plus-one code for use.
While this NFIRSGram is focused on actions taken, the same reasoning can be applied to any multicoded field in which departments can select more than one code and create a plus-one code in the system. The plus-one code is used to further define the base code, but it also means the same thing as the base code.