This paper evaluates the practical implications of recent legislative changes in Australia for residential tenancy and minimum rental housing standards, with a focus on the known risks from mould exposure to health. Specifically, the study examines the use of particulate matter (PM) measurements as a surrogate index for mould spores during residential indoor air quality assessments. The findings indicate that PM10 is a useful surrogate index for mould spores, while PM2.5 is less reliable due to size differences between PM2.5 and mould spores. The paper also investigates the relationship between particulate matter, mould spore sizes, and ambient air quality by reviewing relevant literature and presenting case studies from various Australian and international sources. Overall, the study highlights the importance of early detection during onsite inspections to minimize health hazards related to mould and dampness and to improve indoor air quality in residential tenancy spaces.