By Laura Ampollini, graduate student, DeCarlo Group, Drexel University.
Ammonia, NH3, was one of the gas phase chemicals measured during the HOMEChem experiment. Using high time resolution measurements of ammonia, many activities, such as cooking, cleaning and human occupancy, were monitored better understand how the things we do in our homes affect the air that we breathe. Since ammonia concentrations are much higher indoors than outdoors, there must be indoor sources which emit ammonia. We know that ammonia is emitted from cleaning products, building materials, tobacco smoke, cooking activities, and humans (through exhaled breath and sweat). By correlating measured ammonia concentrations with the activities performed in the house it was possible to better understand the specific factors and processes affecting indoor ammonia concentrations.
Let’s take a brief look at the main results: First, in the absence of primary sources, the trend of ammonia followed the trend of the ambient temperature and cycled with the HVAC system, decreasing when the AC was on and increasing when the AC was off. This behavior is due to the fact that the water available in the surface of the cooling coil and will remove ammonia from the gas phase (a loss), but when the AC turns off and the water evaporates the ammonia is re-released to the gas phase.
The cooking experiment that most affected ammonia was the Thanksgiving dinner, which involved the preparation of a typical American dinner with turkey, roasted brussels sprouts with pancetta, smashed sweet potatoes with marshmallows, cranberry sauce, and stuffing. During this activity ammonia spiked each time the oven was opened while there was meat cooking inside (turkey or pancetta), reaching concentrations that were four times higher than the mean background concentration. We associate this ammonia source with the thermal decomposition of amino acids contained in meat (vegetarian stir fry activities did not increase ammonia).
Ammonia is a very popular household cleaner and thus the cleaning experiment involved spraying an ammonia solution on surfaces and floors which were also mopped with vinegar. During these activities, ammonia reached concentrations fifty times higher than the mean background concentration! The maximum concentration reached during the cleaning activity was the highest concentration found over the entire experiment. No need to worry though…if you are cleaning your house carefully following the product instructions, just leave the windows open and this will increase the air exchange rate and decrease indoor concentrations that may be harmful to your health!
The last activity that was analyzed in this study was the Open House day where three tours of between 15-25 people visited the UTest House. During this “Occupancy activity” ammonia reached concentrations three times higher than the mean background concentration. This result underlines how important it is to be able to quantify human emissions in crowded indoor places, especially in the summer when perspiration levels are much higher!
Read the associated paper here:
Ampollini, Laura, Erin F. Katz, Stephen Bourne, Yilin Tian, Atila Novoselac, Allen H. Goldstein, Gregor Lucic, Michael S. Waring, and Peter DeCarlo. “Observations and Contributions of Real-time Indoor Ammonia Concentrations During HOMEChem.” Environmental science & technology (2019).
And another paper related to HOMEChem here:
Delphine K. Farmer, Marina E. Vance, Jonathan P. D. Abbatt, Andrew Abeleira, Michael R. Alves, C. Arata, Erin Boedicker, Stephen Bourne, Felipe Cardoso-Saldana, Richard Corsi, Peter F. DeCarlo, Allen H. Goldstein, Vicki H. Grassian, Lea Hildebrandt Ruiz, Jose L. Jimenez, Tara F. Kahan, Erin F. Katz, James M. Mattila, William W. Nazaroff, Atila Novoselac, Rachel E. O’Brien, Victor W. Or, S. Patel, Sumit Sankhyan, Philip S. Stevens, Yilin Tian, Michael Wade, Chen Wang, Shan Zhou, and Yong Zhou. Overview of HOMEChem: House Observations of Microbial and Environmental Chemistry, Environmental Science: Processes & Impacts, Environ. Sci.: Processes Impacts, 2019.