The safe level for formaldehyde is 0.75 ppm averaged over an 8 hour work day according to the US Occupational Safety and Health Administration (OSHA). Most homes have a level that is less than 0.03 ppm of formaldehyde in the air. For total VOC concentration measured by a consumer level meter, the Temtop 1000S+ the safe level is up to 0.6 mg/m3. Please see this article for further details-VOCs and Health.