What is necessary for an air-purifying device to be approved for a toxic substance with no warning properties?

For an air-purifying device to be approved for use with a toxic substance that lacks warning properties, a critical requirement is the inclusion of an end-of-service life indicator. This feature is essential because it provides users with a clear and reliable signal indicating when the filter has reached the end of its usable life. In the case of toxic substances without inherent warning properties, such as odor or discoloration, the end-of-service life indicator acts as a safeguard to prevent exposure due to filter saturation.

Without this indicator, individuals may mistakenly believe they are protected when, in fact, the device may no longer be effective. This is particularly important in environments where the risk of exposure to harmful contaminants is high, as it enhances overall safety and allows for timely replacement of filters, thereby ensuring continued protection.