Picarro Blog

Real-Time Indoor Air Measurements of Ammonia Part 1: iCHEAR

Date: September 5, 2019

At Picarro, we enjoy hearing how research groups are using our systems in their projects. In this 2-part blog series, we present a short summary of two research efforts that fall under the Sloan Foundation’s Chemistry of Indoor Environments (CIE) program:  The Indoor Chemical Human Emissions and Reactivity (iCHEAR) and House Observations of Microbial and Environmental Chemistry (HOMEChem), both part of the Indoor Chem Project (https://indoorchem.org/). In part 1 of this blog series, we explore how iCHEAR used a Picarro G2103 analyzer to provide real-time measurements of ammonia emissions to separate the contribution of exhaled and dermally emitted pollutants. What proportion of human emissions do you think can be measured and what proportion remain “missing”? Read on.


The United States Environmental Protection Agency (US EPA) has estimated that an average American will spend 93% of their life in indoor spaces and environments – 7% of which will be spent in personal vehicles (Klepeis et al., 2001 – Nature). While these statistics are likely to differ across regions and levels of development around the world, they highlight the importance of understanding and quantifying emissions and exposures from indoor environments. The complexity of this subject becomes apparent once we consider the broad range of indoor spaces (homes, vehicles, workspaces, etc.) as well as the large number of chemical compounds (100,000+) that we may be exposed to.

To address these matters, a large community of regulatory bodies, civil engineering companies, instrument manufacturers and researchers has been established over the years. However, a very small subset of this community is interested in reexamining our fundamental understanding of indoor air quality. It is this type of research that has, and will, drive future exposure and emissions regulations, building designs and measurement technologies. Picarro is therefore proud to support a key research effort in this field – the Alfred P. Sloan Foundation’s Chemistry of Indoor Environments (CIE) program (https://sloan.org/programs/research/chemistry-of-indoor-environments). We have engaged with several key researchers whose objective is to achieve an important strategic goal of the program: “Advance capacity for discovery through development of new tools for collection, sampling, analysis, and visualization.”

iCHEAR Denmark



iCHEAR (Indoor Chemical Human Emissions and Reactivity) is a Sloan-funded collaborative research project designed to examine the role of humans and human emissions on indoor air chemistry. It is led by research group leader Jonathan Williams (Max Planck Institute for Chemistry) in collaboration with Pawel Wargocki and Gabriel Bekö (Department of Civil Engineering, Technical University of Denmark-DTU) at the International Centre for Indoor Environment and Energy (ICIEE). iCHEAR investigates exhaled, dermally emitted and overall human emissions in carefully controlled stainless steel twin climate chambers (see photo above) under different conditions of clothing, temperature, relative humidity and ozone and their impact on OH reactivity.



Chemical species are characterized using state-of-the-art proton transfer reaction time-of-flight mass spectrometry (PTR-TOF-MS) and an on-line gas chromatography - mass spectrometer (GC-MS), together with traditional sampling on a sorbent and subsequent analysis on a GC-MS. Other measurements in the study include a measure of the concentration of particles down to 1 nm, pollutants as well as biological matter adsorbed on surfaces.

Finally, the measurements include quantifying emissions of carbon dioxide and ammonia emitted by humans under different experimental conditions. Overall, all these measurements allow for the first-ever estimation of the total OH reactivity–based budget of the human- influenced indoor environment. The study will separate the contribution of exhaled and dermally emitted pollutants, and will reveal what proportion of human emissions can be measured and what proportion remains “missing.” The role clothing plays in affecting process in the chamber is going to be investigated as well.


Left GraphRight Graph


The Picarro G2103 analyzer provides real-time measurements of ammonia emissions (red line) from the volunteers under well-characterized conditions. Although ammonia is emitted by humans and has a large impact on indoor acid/base chemistry, its emission from human occupants have been poorly characterized. These measurements enable researchers to determine the rate at which the volunteers emit ammonia under different temperature and relative humidity conditions. They also enable ammonia emissions from breath to be separated from those in dermal off-gassing. Early results show that ammonia concentrations are substantially higher at the higher temperature condition and more exposed skin (higher emission on the top plot when compared to the plot on the bottom).