Unfortunately, there are no pre-defined “safe levels” for airborne mold in Canada.
Mold is ubiquitous and can be found in almost every environment. Each individual within these environments will have varying immune systems, pre-existing medical conditions, etc. As such, determining what is “safe” or “unsafe” will vary considerably and will determine on a wide array of variables that have not been established by exposure levels or values.
The industry standard is to determine if the environment contains a normal indoor fungal ecology. Typically, baseline or control samples are collected outside of the property, to establish the outdoor spore types and concentrations.
Indoor air samples are then compared to the outdoor baseline samples. Often, spores found indoors are identical to the outdoors, which is normal. However, if the concentration levels are higher indoors then outdoors, this can be indicative of an abnormal indoor fungal ecology and will need to be assessed further to determine causes and solutions. An air quality assessment should always be accompanied by a visual & diagnostic inspection.
If the spore types found indoors are unique to the indoor space (meaning, they were not found outdoors), or if the indoor spore types are toxigenic species, this also indicates an abnormal indoor fungal ecology, and remediation may be required to restore the environment to a normal, indoor fungal ecology.