A gas volume is affected by the barometric pressure, environmental temperature and the presence of water vapor.
Descriptors for Gas Volumes Based on Environmental Conditions
|
Term |
Conditions |
|
ATPS |
ambient temperature and pressure, saturated with water vapor |
|
ATPD |
ambient temperature and pressure, dry |
|
BTPS |
body temperature and pressure, saturated with water vapor |
|
STPD |
standard temperature and pressure, dry |
Conversion Gas Volume at ATPS to BTPS
gas volume in liters at BTPS =
= (gas volume in liters at ATPS) * (((barometric pressure in mm Hg) - (water vapor pressure in mm Hg)) / ((barometric pressure) - 47)) * (310 / (273 + (ambient temperature in °C)))
where:
• 47 = vapor pressure of water at 37°C
• 273 = degrees Kelvin at 0°C
• 310 = degrees Kelvin at 37°C (body temperature)
Conversion of Gas Volume at ATPS to STPD
gas volume in liters at STPD =
= (gas volume in liters at ATPS) * (((barometric pressure in mm Hg) - (water vapor pressure in mm Hg)) / 760) * (273 / (273 + (ambient temperature in °C)))
Conversion of Gas Volume at ATPD to STPD
gas volume in liters at STPD =
= (gas volume in liters at ATPD) * ((barometric pressure in mm Hg) / 760) * (273 / (273 + (ambient temperature in °C)))
|
|
numerator for pressure |
denominator for pressure |
numerator for temperature |
denominator for temperature |
|
ATPS to BTPS |
BP - (water vapor) |
BP - 47 |
310 |
273 + °C |
|
ATPS to STOD |
BP - (water vapor) |
760 |
273 |
273 + °C |
|
ATPD to STPD |
BP |
760 |
273 |
273 + °C |
Specialty: Pulmonology
ICD-10: ,
