Conventional EBC pH studies also fail to consider or measure the dilution of ALF by condensed water vapor, which is large and variable (∼ 5,000-20,000 fold). The effect of nonvolatile acids in ALF on EBC pH will obviously be less when the dilution is increased. In view of the dominance of oral NH3 on EBC pH, investigators should measure specific ions in EBC (eg, lactate), indicating metabolic acids from the ALF. Furthermore, sensitive amylase measurements should be routinely made to estimate salivary contamination.3 Some low EBC pH values that have been reported may reflect acid reflux, suggesting that gastric markers should also be measured. Efforts to remove CO2 by bubbling argon through the EBC1,2 are unwise because measurements are not made of the effects of purging on CO2, NH4+/NH3, water, or other volatile constituents. Unless these problems are addressed, it is unlikely that EBC pH will ever become a reliable indicator of pulmonary airway acidosis or inflammation. The expenditure of additional time and scarce resources on conventional EBC pH measurements would, therefore, seem unjustified.