In Chapter 5 in NFPA 2001, edition 2018

There is a table, Table 5.5.3.3 Atmospheric Correction Factors.

¿What would be my correction factor if my equivalent altitude is over 14,000 ft?

In Table 5.5.3.3, the atmospheric correction factor is absolute enclosure pressure above sea level divided by absolute pressure at sea level.

You can interpolate the above table for 14000 ft above sea level.

The equation for finding the interpolated value can be written as y = y1 + ((x – x1)/(x2 - x1) * (y2 - y1))

X = 14,000 ft

X1 = 10,000 ft

X2 = 15,000 ft

Y = absolute pressure (psi) at 14,000 ft

Y1 = 10.108 psi

Y2 = 8.297 psi

Plug in the numbers and calculate.

Y = 10.108 + ((14000-10000)/(15000-10000) * (8.297-10.108)

Y =8.659 psi at 14,000 ft

Calculate the atmospheric correction factor = 8.659 / 14.696 = 0.589 at 14,000 ft

In Table 5.5.3.3, the atmospheric correction factor is absolute enclosure pressure above sea level divided by absolute pressure at sea level.

You can interpolate the above table for 14000 ft above sea level.

The equation for finding the interpolated value can be written as y = y1 + ((x – x1)/(x2 - x1) * (y2 - y1))

X = 14,000 ft

X1 = 10,000 ft

X2 = 15,000 ft

Y = absolute pressure (psi) at 14,000 ft

Y1 = 10.108 psi

Y2 = 8.297 psi

Plug in the numbers and calculate.

Y = 10.108 + ((14000-10000)/(15000-10000) * (8.297-10.108)

Y =8.659 psi at 14,000 ft

Calculate the atmospheric correction factor = 8.659 / 14.696 = 0.589 at 14,000 ft