I am trying to use equation 7 & 8 from a fire safety engineering journal to determine the transmittance of a radiant heat flux through the atmosphere - https://ws680.nist.gov/publication/get_pdf.cfm?pub_id=909662

The math seems quite simple and is a fourth order polynomial equation. I have created a spreadsheet to solve the equations.

However, when I have entered the example given in the journal of using an air temperature of T 288K and a relative humidity of 51%, flame temperature of 1300K and path of 200m into my spreadsheet I cannot end up with a transmittance of0.75 as given in the example.

Could someone please advise what they end up with for a0, a1, a2, a3, a4 so ifI can confirm my results. Otherwise, I am happy to provide a link to my spreadsheet if you would like to review.

Any help is much appreciated.

Regards.