“…Average PEM indoor mean exposure (unadjusted for cofactors) was increased 2.59 ppm (134%) by gas stove operation, 1.59 study participants, and 0.41 ppm (22%) by attached garages. [Arithmetic averages are used throughout this paper for two reasons: the statistical tests are based upon the distribution of sample averages which converges to normality as the sample size increases and the arithmetic mean is more appropriate for characterizing exposure (16). ]…”