Neutralizing Aminesin Boiler Steam and Humidified Indoor Air

Andrew Gomes1, Ye Tao1, *, Abdul Bhuiyan1, Don Guan1, Farhad Memarzadeh1
1 National Institutes of Health, Division of Technical Resources, Bethesda, Maryland 20899, United States

© 2021 Gomes et al.

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address correspondence to this author at National Institutes of Health, Division of Technical Resources, Bethesda, Maryland 20899, United States; Tel: 2402054686; E-mail:



The health and comfort of the indoor population have been impacted by the humidity. While people are increasingly spending more time indoors, the presence of pollutants and lack of proper humidification in indoor air have significant risk factors that may lead to multiple health problems.


By applying the right air purification and/or humidification system, the adverse effects of poor indoor air quality can be minimized. Direct steam addition is a common technique to humidify the indoor air of a building. Carbon dioxide or other acidic process contaminants may dissolve in steam or steam condensate that will consequently decrease the pH and make it corrosive for the steam distribution system. To avoid that, neutralizing amines are added to steam that keeps the pH neutral or slightly alkaline(pH 7.5-9.0). However, neutralizing amines have some toxic effects. OSHA, FDA, and NIOSH prescribe maximum concentration limits for them in indoor air. The Central Utility Plant (CUP) of National Institutes of Health (NIH) uses a 50:50 blend of cyclohexylamine and diethylaminoethanol as neutralizing agents for the steam.


The CUP at NIH presents the results of monitoring the concentration level of amines through mass balance, online monitoring at specified location of the steam distribution system and field measurement in humidified indoor air at buildings on campus.


Through theoretical calculation backed up by field measurement, the amine concentration of indoor air is determined to be well below the FDA regulated limits.