Source removal comes first
The useful question is not how to mask an odor, but which materials absorbed contamination and whether they can be cleaned, sealed, or need removal.
Porous materials can complicate cleanup
Carpet, padding, subfloor, drywall, furniture, and other absorbent materials can retain contamination. The appropriate response depends on the extent and depth of impact.
Connected to unattended-death cleanup
Decomposition and odor remediation often overlap with unattended-death cleanup, but this page focuses specifically on persistent contamination and odor-source issues.