Protection of personnel and buildings Procedures to protect the general public and those carrying out stonecleaning work, the building itself and its environment from any chemical contamination should be in place before any cleaning commences.Suitableprotectiveclothingmust be worn by operatives when handling,mixing and rinsing off chemicals. Protective clothing should be washed after use to ensure no residual chemicals remain on clothing. Acidic and alkaline chemical cleaners can cause serious injury in both their liquid and vapour form. Injury can be caused to the skin and eyes and also to the respiratory tract. Adequate first aid equipment should be on site and personnel should be trained in its use. If hydrofluoric acid based chemicals are being used, hydrofluoric acid burn gel must be readily available.The use of chemical cleaners is subject to the Control of Substances Hazardous to Health Regulations 1988 (COSHH)and the Construction Regulations 1961 and 1966. Those parts of buildings which are not to come into contact with cleaningchemicals (for exampleglass)should be properly protected by material which will not be attacked by the chemicals (Plate5.13). Scaffolding should be sheeted to prevent the drift of any airborne chemicals. The ends of scaffolding tubes should be capped to prevent chemical fluids or vapours entering them. Protective sheeting should be designed and applied to the collection and runoff flow of residual chemicals to avoid the risk of concentration and contamination. Chapter 7 provides a summary of the main health and safety regulations which apply to stonecleaning work.
Dilution of chemicals Reference should always be made to the appropriate health and safety legislation. The manufacturers of stonecleaning chemicals issue general guide-lines on the dilution of their chemicals. Care must be taken to dilute any chemicals in accordance with manufacturers instructions. Ideally concentrated chemicals should not be stored or mixed on site. Chemicals which are supplied in dilute form by the manufacturers reduce the risks involved in handling and mixing. It is advisable to test the effects of varying the concentration of chemicals recommended by manufacturers, on test panels, before application to the whole buiIding. This may involve further dilution to achieve anappropriate working strength.
Environmental concerns The potential environmental effects of the use of chemicals should be considered. Any regulations regarding the discharge of effluents into the public drainage system need to be checked. Effluent run-off from the building needs to be monitored so as to minimise any local environmental damage. Airborne chemicals can cause damage to people and property (e.g.etchingof glass, damage to car paintwork). Solid residues (e.g. poultice) also need to be disposed of so as not to cause problems to public drains.