This study used the so-called ‘gold standard’ method of the Randomized Controlled Trial (RCT) to look at whether regular (once every 6 weeks for one full year) thorough cleaning of all accessible, finished floors using HEPA filter equipped vacuum cleaners would have a measurable effect on children’s blood lead levels. The treatment group of 55 homes received the cleanings, while 56 control homes did not. Analysis of children’s blood lead and floor dust lead concentrations from all of the study homes found that there was no statistically significant benefit from the regular intensive floor cleaning on blood lead, and the improvements in floor dust lead loading from study start to finish were small. An assessment of recontamination was performed on 18 of the treatment group homes following the final cleaning visit. This found that on average, it took 2.5 to 3 weeks for carpet lead loadings to return to the levels there were at prior to the final vacuuming, which suggested that thorough cleaning only once every 6 weeks might not be frequent enough to make a difference in many homes.