To minimize formaldehyde exposures at home, make sure any wood furniture or fixtures that use particleboard are laminated or otherwise coated, choose exterior- rather than interior-grade pressed wood products for remodeling and be sure that areas where you are using products containing formaldehyde are well ventilated.
Formaldehyde can be detected in human breath and, like "breathalyzer" test, is a reliable indicator of formaldehyde levels in blood. It can be also detected in urine. In an older study (Berthold Moser, et al., Respiratory Physiology & Neurobiology, Vol. 145, Issues 2-3, February 2005), the median level of formaldehyde in human breath was 4.3 parts per billion (ppb) with levels of 6.3 ppb, 40 ppb and 73 ppb of the 75th, 97.5th and maximum percentiles, respectively.