System Sensor is pleased to provide this Equivalent Facilitation calculator. The calculator was programmed to assist you in the design of audible/visible notification device circuits.

There are no express or implied warranties of any kind with this calculator. System Sensor does not provide any design or engineering services. Users of this calculator are solely responsible for their own selection and use of products based upon information contained in this calculator and any calculations from this calculator. System Sensor shall have no liability.

This calculator uses data provided by the user to perform the calculations described in Chapter 7 of the 2002 edition of NFPA 72, which permits the use of a performance-based alternative in lieu of tables for spacing ceiling mounted audible/visible devices. These calculations are described in Section 7.5.4.3 as follows and are to be provided to the authority having jurisdiction:

To calculate performance based strobe coverage, the inverse square law is used to calculate the illumination at each of the angles in the horizontal and vertical planes per UL 1971 and the effect of polar distribution is included using the minimum percentages in UL 1971 or actual test results recorded by the Listing organization (per Section 7.5.4.3.2).

The calculated illumination is required to be at least 0.0375 lumens/square foot at any point within the covered area (per Section 7.5.4.3.1).

The calculation points are in the horizontal and vertical planes in 5 degree increments per UL 1971 (to comply with 7.5.4.3.2).

For the effect of polar distribution (rated candela at each angle), the UL 1971 minimum percentages are used for the calculations. UL 1971 does not provide ratings for each angle based on actual test results.