General Ventilation in the Workplace Guidance for Employers

INTRODUCTION1 Everyone working in offices, shops,factories, hospitals, laboratories etc requires aminimum standard of fresh air to produce ahealthy working environment. One way thatthis can be provided is by effective generalventilation. This guidance is aimed atemployers to help them understand thebenefits and limitations of effective generalventilation in the workplace.2 This guide defines general ventilation andgives information on fresh air requirements. Italso looks at the principles and use of generalventilation as a means of controlling exposureto substances hazardous to health as requiredunder the Control of Substances Hazardous toHealth Regulations (COSHH) 1999 1 and theassociated Approved Codes of Practice 2 . Itgives the current ventilation standards andadvises you, the employer, on how to achieveeffective general ventilation in your workplace.It outlines the methods used to assess theeffectiveness of your ventilation system andsets out the legislation on what you arerequired to do to ensure effective ventilation.The guide also tells you where to get furtherinformation and help.3 This guide does not deal with ventilation of:processes requiring local exhaustventilation (LEV);some specialised premises, for examplelivestock buildings, confined spaces, minesor flammable stores; ordomestic premises.4 This guide does not deal with systems forcontrolling smoke and combustion productsfrom accidental fires or the consequences ofcondensation and mould growth.WHAT IS GENERALVENTILATION?5 General ventilation or 'dilution' ventilationis a term used to define the flow of air into andout of a working area, for example an officespace, so that any contaminants are diluted byadding some fresh air. This can be provided by:6Natural ventilation which relies on windpressure and temperature differences tomove fresh air through a building and isusually not fully controllable; and'Forced' or mechanical ventilation which usesmechanical supply and/or extraction toprovide fresh air and is controllable(see Figure 1).WHY IS FRESH AIRREQUIRED IN THEWORKPLACE?You need to provide fresh air to:provide oxygen for breathing in and toremove carbon dioxide from breathing out;remove excess heat or, if conditioned,provide heat eg in winter and keep acomfortable temperature;dilute and remove body and other types ofodours (eg food); and1