Human ammonia emission rates under various indoor environmental conditions

Ammonia (NH₃) is typically measured at mixing ratios of 50 parts per trillion (ppt) to 5 parts per billion (ppb) in outside air, while its mixing ratios are approximately an order of magnitude larger indoors. In both outdoor and indoor environments, NH₃ is the dominant basic species. High NH₃ concentrations (> 25 ppm) are associated with adverse health effects.
Considering that humans spend more than 90% of their life in indoor environments, coupled with the strong impact that NH₃ has on indoor acid-base processes (Nazaroff and Weschler, 2020), it is important to determine the rates and predominant driving factors for indoor NH₃ emissions from humans beings which are potent mobile sources. In this study, we have assessed human NH₃ emission rates (from whole body, from skin, from breath) as a function of temperature, clothing (skin coverage), age, relative humidity and ozone levels. Real-time measurements were made with five groups each consisting of four healthy individuals, housed within a controlled climate chamber, using a cavity ringdown spectrometer. This study is part of the Indoor Chemical Human Emissions and Reactivity (ICHEAR) project.