Healthy children have a lower range of NO values, indicating age-dependent variability. Height was found to be the best independent variable for the regression equation for exhaled NO. On average, an increase in height from 120 to 180 cm correlates to an increase in normal FENO levels from 7 to 14 ppb. (Malmberg 2006)

For adults, normal values of FENO can also be predicted on the basis of gender, height and age. (Olin 2006)