PE-PUR foam — polyester-based polyurethane — was used by Philips Respironics as a sound-dampening material inside CPAP and BiPAP devices. Under normal use conditions — especially heat above 90°F, high humidity, or exposure to ozone (from ozone-based CPAP cleaners) — this foam undergoes chemical degradation and releases volatile organic compounds (VOCs) and particulate matter. Because the foam is positioned in the device's airflow pathway, these breakdown products are inhaled directly by users during every sleep session.

FDA testing identified toluene diisocyanate (TDI — classified as a possible human carcinogen by IARC), dimethylformamide (DMFA — a known animal carcinogen with human evidence), diethylene glycol, and N,N-dimethylacetamide among the over 200 compounds released. TDI is directly linked to respiratory cancers; DMFA and DMAC are linked to liver and systemic toxicity; diethylene glycol causes renal toxicity at high exposures. The combination of carcinogens released — and the nightly, multi-year duration of exposure for typical CPAP users — creates a strong basis for causation in cancer claims.