The Evaluation of Short-Term Water Misting of Room Air in Reducing Airborne Dust after Renovation Work.

Abstract

To shorten the time for airborne dust concentration to be reduced to a lower level after a renovation task has been completed, a short-term water misting method was assessed. A short-term water misting method is based on low water consumption to avoid harmful wetting of materials. The method is considered similar to a general ventilation method that dilutes work-generated airborne dust concentrations. Thus, short-term misting is not intended to replace the source control measures. Airborne dust removal by the short-term water misting performed after dust generation was evaluated in a controlled laboratory settings by comparing PM10 decay and inhalable dust concentrations between a control and misting tests (average water flow = 0.22 l min-1) of 2 and 4 min. A portable handheld misting device was used. The practicability and effectiveness of the misting technique as a supplementary control measure was verified in the three field cases. In laboratory tests, reductions in airborne PM10 and inhalable dust were 30% and 28%, avoiding condensation of water to surfaces. In the field, inhalable dust concentrations were reduced by 86-95% after an hour from the misting, whereas ventilation alone was calculated to dilute dust concentrations by 18-39%. Average clean air delivery rates varied from 0.03 to 0.07 m3 s-1. Short-term misting after a dust-generating task is an effective measure to control the airborne dust after dust-producing tasks in environments where an effective air exchange for dust removal is not a feasible alternative. The information obtained from the study is beneficial to construction and renovation project management personnel and field practitioners.