California businesses are required to review applicable orders and guidance from the state and respective local health departments related to COVID-19 hazards and prevention. This includes the CDPH Interim Guidance for Ventilation, Filtration, and Air Quality in Indoor Environments. The CDC also offers ventilation guidance.
After reviewing the guidance documents, an employer must take reasonable steps to improve the air quality within their facility. An employer will want to consult with appropriate professionals, such as HVAC contractors or building engineers, before undertaking significant changes.