Product review (5 stars): Great mold monitors!
We bought 4 of these to monitor a long term problem with mold around our floor registers that required duct cleaning, replacement, repair and resizing. Their readouts are not identical, when together, but cover a span of about 5 percent, which is ok with us. We have a 2900 sq ft rancher, 3BR,  4BR, a heat pump and three propane heat sources as backup for power losses. We've had the monitors for 2 months as we transition through spring. We dispersed these widely and moved them about, finding humidity varies about 10% from highest to lowest areas. Highest was in a bedroom most distant from a bathroom and kitchen, with two floor registers! Most of the time the humidity was close to 60% and was best kept about 55% or lower with HVAC set for 1 Cycle Per Hour (default on our Honeywell thermostadt was 3 CPH).  The monitors have been a great buy and are helping us deal with humidity issues. We hope we'll now be able to stop mold growth during the humid summer and monitor moisture in the house on a regular basis. Anyone with mold issues should have several of these.