An indoor air quality evaluation in a residential retrofit project using spray polyurethane foam

ABSTRACT

Understanding of indoor air quality (IAQ) during and after spray polyurethane foam (SPF) application is essential to protect the health of both workers and building occupants. Previous efforts such as field monitoring, micro-chamber/spray booth emission studies, and fate/transport modeling have been conducted to understand the chemical exposure of SPF and guide risk mitigation strategies. However, each type of research has its limitation and can only reveal partial information on the relationship between SPF and IAQ. A comprehensive study is truly needed to integrate the experimental design and analytical testing methods in the field/chamber studies with the mathematical tools employed in the modeling studies. This study aims to bridge this gap and provide a more comprehensive understanding on the impact of SPF to IAQ. The field sampling plan of this research aims to evaluate the airborne concentrations of methylene diphenyl diisocyanate (MDI), formaldehyde, acetaldehyde, propionaldehyde, tris(1-chlor-2-propyl)phosphate (TCPP), trans-1-chloro-3,3,3-trifluoropropene (Solstice^TM), and airborne particles. Modifications to existing MDI sampling and analytical methods were made so that level of quantification was improved. In addition, key fate and transport modeling input parameters such as air changes per hour and airborne particle size distribution were measured. More importantly, TCPP accumulation onto materials was evaluated, which is important to study the fate and transport of semi-volatile organic compounds. The IAQ results showed that after spray application was completed in the entire building, airborne concentrations decreased for all chemicals monitored. However, it is our recommendation that during SPF application, no one should return to the application site without proper personal protection equipment as long as there are active spray activities in the building. The comparison between this field study and a recent chamber study proved surface sorption and particle deposition is an important factor in determining the fate of airborne TCPP. The study also suggests the need for further evaluation by employing mathematical models, proving the data generated in this work as informative to industry and the broader scientific community.

KEYWORDS:

• Airborne particles
• field monitoring
• industrial hygiene
• methylene diphenyl diisocyanate
• tris(1-chlor-2-propyl)phosphate

Acknowledgment

The authors appreciate the helpful comments given by Dr. Xiaoyu Liu at the USEPA and Dr. Dustin Poppendieck at NIST. We also thank Mr. Chris Hazen and Mr. Joe Hazen for allowing us to conduct sampling in their home and Mr. Richard Romero's coordination on this project. Shen Tian works at Covestro and is also a PhD candidate at the University of Pittsburgh and Covestro supports his research through tuition payment. Covestro is a chemical raw material supplier of methylene diphenyl diisocyanate. Covestro also supplied raw materials to produce the two-component SPF system applied in this renovation project.