Dust Suppression

Why water, and why it is not optional

Cutting, grinding or drilling concrete, stone, brick or screed throws off respirable crystalline silica, a dust fine enough to travel deep into the lung. Prolonged exposure leads to silicosis and raises lung cancer risk, which is why the exposure limit for it is among the tightest applied on a British site.

Under COSHH, the duty is to prevent exposure or, where that is not reasonably practicable, to control it at source. Water suppression is control at source: the dust is wetted as it is created, so it never becomes airborne. That is a different and better thing from a mask, which protects one person after the dust is already in the air.

Water does not remove the need for respiratory protection on higher-risk cuts, but a job done dry with only a mask is the arrangement HSE inspectors look for.

Choosing a bottle size

Bottles here come in 8, 10 and 14 litres. The trade is carrying weight against refill stops, and water is a kilogram a litre, so a full 14 litre bottle is a serious lift.

The practical rule: 8 litres for working at height, on a ladder or moving between short cuts; 10 litres as the general choice; 14 litres where the work is stationary and sustained and refilling means walking somewhere. A transport trolley is available for the larger bottles, which is worth having if the bottle moves around a site all day.

Using it properly

Pressurised bottles need pumping up before they deliver a consistent flow, and pressure drops as the bottle empties. A bottle that has not been pumped since the last cut gives a dribble, and a dribble does not suppress dust.

Set the flow so the cut stays visibly wet through the whole cut rather than damped at the start. Slurry running off the work is roughly the right sign. Too little water and you are making a paste that clogs the blade; too much on a vertical face and it runs away before it reaches the cutting point.

Direct the feed at the blade or bit where it enters the material, not at the surface nearby.

Looking after them

These are pressure vessels with seals, and they fail from neglect rather than use. Release the pressure at the end of the day rather than leaving a bottle charged overnight, rinse the tank if the water has been drawn from a site butt, and drain it before a frost, because ice splits a tank and a split tank cannot hold pressure.

Spare parts are listed for the 10 and 14 litre bottles, including hoses, seals, valves and hand pump parts, so a perished O ring does not mean buying a new bottle.