Indoor temperature and humidity in New York City apartments during winter

Background: Concerns about indoor residential humidity have largely centered on dampness prevention. Overly dry air, however, may favor the survival of some viruses and hence respiratory infections. Many residents employ portable humidifiers to humidify their home environment, yet the effect of these humidifiers on indoor humidity is not known. Methods: We monitored indoor temperature and humidity in 34 apartments in New Yak City during winter 2014-2015. We combined information from the monitors with surveyed information on building, household, and apartment-level factors and with information on household humidifier use. Using multilevel regression models, we investigated the role of these factors on indoor absolute humidity levels during the winter. Results: Mean indoor vapor pressure (a measure of absolute humidity) was 6.7 mb in the surveyed homes during the winter season. Ownership of a humidifier was not associated with higher indoor humidity levels; however, larger building size (above 100 units) was significantly associated with lower humidity. The presence of a radiator heating system was non-significantly associated with higher humidity. Conclusions: The wintertime indoor environment in this sample of New York City apartments is dry. Future research is needed to evaluate the effectiveness of portable humidifiers in the home and to clarify the relationship between dry indoor air and the transmission of viral infections. (C) 2017 Elsevier B.V. All rights reserved.