This calculator computes rates of oxygen consumption (VO_{2}) and/or carbon dioxide production (VCO_{2}) in air or other breathable gas mixture in a closed system (i.e, the animal is sealed in an airtight chamber for some time and metabolism is computed by the change in concentration of O_{2} and CO_{2} between initial and final gas samples). You need to enter:
 chamber temperature, pressure, and relative humidity (when sealed, not at the end of measurements).
 chamber volume
 elapsed time (between taking the initial and final gas samples)
 initial fractional concentrations of O_{2} (FiO_{2}) and CO_{2} (FiCO_{2})
 the change in concentration (in percent) of oxygen and/or CO_{2}, and the respiratory quotient (RQ)
If you measure only one of these two gas species, the program will use RQ to estimate the other. If you measure both O_{2} and CO_{2} concentration changes, the program will optionally use O_{2} in the calculation of VCO_{2}.
NOTE: it is assumed that sample gas is dried before measurement, and the default settings are:
 Initial O_{2} concentration (FiO_{2}) = .2095
 Initial CO_{2} concentration (FiCO_{2}) = .0004
 CO_{2} is absorbed prior to O_{2} measurement
 VCO_{2} is computed from VO_{2}, if oxygen is measured, or from RQ otherwise
Equations notes:
 STP = standard temperature and pressure (0°C, 760 torr)
 Δ[O_{2}] = fractional change in O2 concentration
 Δ[CO_{2}] = fractional change in CO2 concentration
 FeO_{2} = FiO_{2}  Δ[O_{2}]
 FeCO_{2} = FiCO_{2} + Δ[CO_{2}]
VO_{2} equations:
 CO_{2} is absorbed:
VO_{2} = STP volume * Δ[O_{2}] /(1  FeO_{2})
 CO_{2} NOT absorbed, compute from Δ[CO_{2}]:
VO_{2} = STP volume * (Δ[O_{2}]  (FeO_{2} * Δ[CO_{2}])/(1  FeO_{2})
 CO_{2} NOT absorbed, compute from RQ:
VO2 = STP volume * (Δ[O_{2}] /(1  FeO2 * (1RQ))
VCO_{2} equations: NOTE: at typical Δ[CO_{2}], different equations have little effect on calculated VCO_{2}
 from RQ:
VCO_{2} = STP volume * Δ[CO_{2}]/(1  FeCO_{2} * (1(1/RQ)))
 from VO_{2}:
VCO_{2} = STP volume * (Δ[CO_{2}]  (FeCO_{2} * VO_{2}))/(1  FeCO_{2})
