chain-saw cover covered covering danger dangers ear-muffs ear-protection equipment feeding grinder helmeted helmets high-pressure improvement machine machinery maintenance men-at-work outdoor-power-equipment power-equipment protection protective-clothing protective-gear pushing risks risky safety safety-colours spray stumpgrinder sunlight sunshine tools tree tree-branches tree-loppers tree-lopping wood-chipper wood-chipping wood-chipping-machine work work-clothes workers workman workmen