Gay-Lussac's Law or Combined Gas Law when volume is constant:
P1/T1 = P2/T2
C = (F - 32) x 5/9
K = C + 273.15
where C, F and K are temperatures in Centigrade, Fahrenheit and Kelvin respectively.
For DOT tubes, pressure is known at 70° F. Pressure at any desired temperature can be calculated using Gay-Lussac's Law.
P1 = 2850 psi
T1 = 70 ° F = 294.261 ° K
T2 = 110 ° F = 316.483 ° K
P2 = ?
P2 = (P1 x T2) / T1 = (2850 x 316.48) / 294.26 = 3065 psi
For calculating volume and weight of gases at certain temperature and pressure, please go to the Gas Calculator page under Technical section of this site.