Cold-freon effect

The most common errors are the inability to coordinate inhalation with MDI actuation, to inhale too quickly, and to exhale without a breath-hold (12,49,50). Crompton (49) identified 215 patients with inadequate inhaler technique. Of these, 50% failed to synchronize aerosol release with inhalation and 36% stopped inhaling when the propellant spray hit the back of the throat. Patients may stop breathing in when propellants impact on the back of the throat and rapidly evaporate, causing almost instantaneous cooling in that area. This is known as the cold freon effect (51). It is difficult to argue with the advice that old patients, young patients, and anyone else should be assumed to be unable to use pMDIs properly unless proved otherwise (49). Nasal inhalation is also a common error among children (51). 

Answer by Author Although I have not had any experience with Freon-blown foams, 1 would suggest that the condensation effects would be similar to that found with other closed-cell materials. In order to minimize or eliminate these effects, it is necessary to provide a perfect gas seal around the insulation and thereby preclude the possibility of air contacting the cold tank surfaces during the cool-down time. 

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