0.5 PPB above threshold

First of all check the units from the lab.  The units are either parts per billion (ppb) or micrograms per cubic meter (ug/M3).  At industrial hygiene standard temperature and pressure a ug/M3 of formaldehyde is 1.228 times a ppb (i.e., 1 ppb = 1.228 ug/M3).  Also, I would ask the lab what level of accuracy they have for the method used (i.e., an accuracy of 10% [typically 95th percentile] would mean the true level is anywehere bewteen 24.75 and 30.25 ppb).  Lastly I would look at the blank which should have been submitted to see if any formaldehyde was detected on the unused media.  If there was you could subtract that amount from the sample result.   To answer your question I would submit and provide a narrative citing some of the issues I discussed previously.  Retesting could result in even higher numbers.