At what relative humidity level does mould growth begin to thrive?

Mould growth begins to thrive at relative humidity levels above 70%. This is because mould requires a certain amount of moisture in the air to proliferate; levels at or above 70% provide an environment conducive to their growth. Mould spores, which are ubiquitous in indoor and outdoor environments, require moisture to germinate and begin growing. When humidity is maintained at levels higher than 70%, the risk of mould development increases significantly, leading to potential health hazards and structural issues.

Understanding this threshold is critical for effective occupational hygiene monitoring, especially in environments where moisture accumulation may occur, such as basements, bathrooms, or industrial facilities where humidity can rise. Maintaining relative humidity below this level is an essential practice in preventing mould growth and ensuring a safe environment.