[en] In recognition of the fact that some field conditions may adversely affect the performance of passive alpha track detectors a French, an Irish and an Italian laboratory carried out an intercomparison of their detectors in three dwellings in each of their countries. Two closed types of detectors (LR-115 and CR-39) and one open faced type (LR-115) were used. A total of 270 detectors, were exposed in the dwellings for a 4 month period to radon concentrations ranging from about 10 to 700 Bq.m^-3. In each house 10 detectors from each laboratory were exposed. A comparison of the results obtained is presented and also, based on the experience gained, a number of recommendations for any future such intercomparisons. (author)