You should rest assured that there has been no mode to determine the maximum possible number of safe reuse for N95 Mask Singapore. You would need to apply a generic number in all cases. It would be pertinent to mention here that safe N95 reuse would be affected by a wide number of variables impacting respirator functionality and contamination with passage of time.
However, the manufacturers of N95 respirators would have specific guidance pertaining to reuse of their product. The recommendation would be designed to provide practical advice so that N95 respirators have been discarded prior to them becoming a considerable risk to contact transmission or their functionality has been reduced.