Shield sprays on the underside of the canopy. NIOSH researchers have observed shield sprays mounted on the underside of the shields, as shown in Figure 3-15 [Rider and Colinet 2007]. These sprays were automatically activated by the position of the shearer to create a moving water curtain in an attempt to contain the dust cloud near the headgate and tailgate drum areas. The location of these underside sprays ranged between the tip of each shield to an area above the spill plate. Each shield was equipped with one or two rows of two sprays. The sequencing of when the sprays were activated and deactivated was mine-specific. When the shield sprays were operational at one mine, researchers observed that they had a negative impact on controlling respirable dust associated with the upwind drum. The shield sprays interacted with the upwind splitter arm sprays, creating turbulence that resulted in a dust and mist cloud rolling into the walkway. Proper on/off sequencing of these shield sprays is critical for these sprays to supplement the directional spray system. Properly aligned sprays directed toward the face with sufficient water pressure and volume have the potential to enhance the envelope of clean air created by the shearer’s directional spray system.