At sea level Patm = 101.325 kPa.
$$ R_{gas} = 8.314 \:
{{( kg.m ^ 2 ) \over \left({ s ^ 2 .K.mol }\right)}}
$$
Gas Density
$$ P_{abs} = {P_{atm} + P_{gauge}} $$
Degree Kelvin
$$ T_{gas_K} = {T_{gas_C} + 273.15} $$
Gas Density
$$ \rho_{gas} = {{( P_{abs} \cdot MW ) \over \left({ z_{gas} \cdot R_{gas} \cdot T_{gas_K} }\right)}} $$
