pCO2 Sample Clauses

pCO2. Alkalinity is estimated from pH assuming an open system in equilibrium with CO2 in the atmosphere. The relatively small differences between indoor and outdoor CO2 concentrations may significantly affect the calculated alkalinity. For this reason, the user is allowed to adjust the pCO2 value (i.e., ambient CO2 concentration in atmospheres). In most natural settings, it is a reasonable assumption that the CO2 concentration will be 10-3.5 atmospheres, but for indoor settings (where many toxicity tests are performed) this might not be the case. CO2 concentrations are typically higher indoors, resulting in a lower pCO2 value. Most indoor air quality standards suggest CO2 to be at concentrations of less than 10-3 atmospheres, so the pCO2 should generally be greater than 10-3.5 and less than 10-3.0 atmospheres. The indoor CO2 concentration depends on the amount of ventilation and respiration occurring in the building, and there would not be any physical effects from CO2 until it reached much higher concentrations than 10-3 atmospheres. Hence, pCO2 values greater than 10-3 atmospheres are possible but not likely.