Table 1. Information related to the mechanical systems and its operating conditions for different areas at each plant, including filter ratings used in the systems and reported as Minimum Efficiency Reporting Values (MERV).

	Site A	Site B	Site C
Processing areas	The fabrication area is pressurized by outdoor air	Only recirculation	Only recirculation
Kill (Slaughter) areas	Exhaust air only	Exhaust + make-up outdoor air	Exhaust + make-up outdoor air
Common areas	Only recirculation	15% outdoor air (with economizer)	Only recirculation
Additional filters/cleaner (in both processing and common areas)	MERV 13 or 16 In-duct GUV (Germicidal Ultraviolet), portable ionizer in some common areas	Upgraded to MERV 13 right before the site measurement	MERV 4 or 8 filters in-unit UV oxidizing air purifying devices