GENERAL VENTILATION - UCU
GENERAL VENTILATIONG U I D A N C EF O RHSG202E M P L O Y E R S
Crown copyright 2000Applications for reproduction should be made inwriting to:Copyright Unit, Her Majesty's Stationery Office,St. Clements House, 2-16 Colegate,Norwich NR3 1BQFirst published 2000ISBN 0 7176 1793 9All rights reserved. No part of this publicationmay be reproduced, stored in a retrievalsystem, or transmitted in any form or by anymeans (electronic, mechanical, photocopying,recording or otherwise) without the priorwritten permission of the copyright owner.This guidance is issued by the Health andSafety Executive. Following the guidance isnot compulsory and you are free to take otheraction. But if you do follow the guidance youwill normally be doing enough to comply withthe law. Health and safety inspectors seek tosecure compliance with the law and may referto this guidance as illustrating good practice.ii
CONTENTSINTRODUCTION1WHAT IS GENERAL VENTILATION?1WHY IS FRESH AIR REQUIRED IN THEWORKPLACE?1Health effects of insufficient fresh air2PRINCIPLES OF NATURAL VENTILATION3WHEN TO USE GENERAL VENTILATIONUse of recirculated airEmergencies456STANDARDS OF GENERAL VENTILATION6Factories, hospitals, laboratories etc6Offices, shops, theatres etc8Standards for gas, coal or oil firedequipment8Air movement8HOW TO ACHIEVE EFFECTIVEVENTILATION IN YOUR WORKPLACE8ASSESSING THE EFFECTIVENESS OFYOUR VENTILATION SYSTEM10Maintenance of mechanical ventilationsystems11WHAT THE LAW REQUIRES YOU TO DO12REFERENCES13FURTHER INFORMATION14HSE Publications14British Standards Institution Publications14Other publications14Useful organisations15iii
4INTRODUCTION1This guide does not deal with systems forcontrolling smoke and combustion productsEveryone working in offices, shops,factories, hospitals, laboratories etc requires afrom accidental fires or the consequences ofcondensation and mould growth.minimum standard of fresh air to produce ahealthy working environment. One way thatWHAT IS GENERALVENTILATION?this can be provided is by effective generalventilation. This guidance is aimed atemployers to help them understand thebenefits and limitations of effective general5General ventilation or 'dilution' ventilationis a term used to define the flow of air into andventilation in the workplace.out of a working area, for example an office2This guide defines general ventilation andgives information on fresh air requirements. Itspace, so that any contaminants are diluted byadding some fresh air. This can be provided by:also looks at the principles and use of generalNatural ventilation which relies on windventilation as a means of controlling exposurepressure and temperature differences toto substances hazardous to health as requiredmove fresh air through a building and isunder the Control of Substances Hazardous tousually not fully controllable; and1Health Regulations (COSHH) 1999 and theassociated Approved Codes of Practice2. It'Forced' or mechanical ventilation which usesgives the current ventilation standards andmechanical supply and/or extraction toadvises you, the employer, on how to achieveprovide fresh air and is controllableeffective general ventilation in your workplace.(see Figure 1).It outlines the methods used to assess theeffectiveness of your ventilation system andWHY IS FRESH AIRREQUIRED IN THEWORKPLACE?sets out the legislation on what you arerequired to do to ensure effective ventilation.The guide also tells you where to get furtherinformation and help.3This guide does not deal with ventilation of:processes requiring local exhaustventilation (LEV);6You need to provide fresh air to:provide oxygen for breathing in and toremove carbon dioxide from breathing out;remove excess heat or, if conditioned,some specialised premises, for exampleprovide heat eg in winter and keep alivestock buildings, confined spaces, minescomfortable temperature;or flammable stores; ordomestic premises.dilute and remove body and other types ofodours (eg food); and1
Extractor fanin roofFresh airsupply fanin wallFigure 1: Mechanical ventilation using fans to supply and extract air7dilute any contaminants caused byfiltered to remove particulates, and shouldworkplace activities (ie the use of 'dilution'have fresh air added to it before beingventilation following a risk assessment).reintroduced into the workplace.Fresh air is 'clean' air which has come from a9When providing fresh air for yoursource outside the workplace. The mainemployees, make sure there are noconstituents of dry air by volume are:uncomfortable draughts from the movement ofair.nitrogen78.08%oxygen20.94%Health effects of insufficient fresh airinert gases0.95%10 Insufficient fresh air may lead to tiredness,carbon dioxide0.03%lethargy, headaches, dry or itchy skin and eye(300 parts per million)irritation in your employees. These symptomsmay also be produced whilst working in poorlydesigned buildings and offices and where8The fresh air' which is brought into yourworkplace should be free of contaminants suchas engine exhaust emissions, or dischargesfrom oil or gas fired flues or extract outlets. Ifyou expect the inlet air to be heavilycontaminated with particulates (eg heavytraffic, smoke etc) then it should be filtered. Airto be recirculated should be adequately2there are unsatisfactory working conditions, forexample the inability of workers to controlcertain aspects of their work. The symptomsare generally worse in buildings where there isnot enough fresh air. These are commonsymptoms of what is generally known as 'sickbuilding syndrome' (SBS).
11 The HSE publication How to deal with sickpressure differences in a building create anbuilding syndrome3 gives information on theupward movement of air or stack' effect.causes of SBS and guidance on how toOccasionally, there can be downward airprevent it.movement if the air is cold.14 Wind forces are affected by wind speed,PRINCIPLES OFNATURAL VENTILATIONwind direction and the shape of the building.Cross-ventilation occurs when wind blows airthrough a room or building which has openings,12 A basic knowledge of the principles offor example windows on opposite sidesnatural ventilation can help you understand(see Figure 2). Single-sided ventilation occurshow to use general ventilation as a way ofwhen there are one or more openings (such ascontrolling exposure to contaminants produceda window and a door] on one side only.in the workplace.15 Stack ventilation may be effective enough13 Natural ventilation is produced by theto carry vapours generated by small-scale hoteffects of temperature and changes in airindustrial processes upwards. They can thenpressure ie wind. Temperature and airbe removed through the roof via roofAir passesthroughbuildingvia openwindowsto removecontaminantsAir entersthroughopenwindowsWindowsclosedAir becomesstagnant ifwindows and doorsshutFigure 2. Cross-ventilation to remove contaminants in an office building3
Vapour laden air rises toroof where it accumulatesor escapes through roof ventIf ventilation is notsufficient, the vapourwill collect in the roofspace or drift back downVapour which doesnot escape may hangin stratified layerCool air enters atlow level throughopen windowsCool air enters atlow level throughopen windowsHot process producingfumesFigure 3: Stack ventilation to remove vapours through roof ventilatorsventilators or extraction fans. If cooler air comesin at a low level, it will displace the warm risingcontaminated air, ie displacement ventilation(see paragraph 20)(see Figure 3).WHEN TO USEGENERAL VENTILATION16 To ensure a well ventilated workplace youshould provide general ventilation that removesstale, contaminated, or hot and humid air so thatyour employees do not suffer any ill-healtheffects. There is guidance on how you canensure thermal comfort at your workplace in the4HSE publication Thermal comfort in the workplace.417 You may consider using effective naturaland/or mechanical general ventilation toprovide the fresh air supply.18 As an employer, if you carry out industrial ornon-industrial work processes (eg hairdressing,catering) you will be required to undertake arisk assessment under the COSHH Regulations.This means assessing the risks to health of youremployees who may be potentially exposed tosubstances hazardous to health. You may thenneed to prevent or adequately control suchexposure.
19 If the contaminant is of such a low toxicitythe contaminant has a low toxicity (see theand produced in such low concentrations that itChemicals (Hazard Information andwould be impractical and costly to use localPackaging for Supply) (Amendment)exhaust ventilation, you may decide to useRegulations 19996);general ventilation as part of your controlstrategy (see HSE publication COSHHEssentials).5 However, if there are a smallthe contaminant is produced at auniform rate;number of well-spaced contaminant sources,the workers are positioned at 90 to the airusing LEV may be more cost effective thanflow (the contaminant air must not be drawngeneral ventilation (see Figure 4). There mayor blown towards the faces ofbe instances where intermittent exposure to athe operatives);substance exceeds the assigned OccupationalExposure Limit (OEL), for example duringwelding and paint spraying. In this case, youthe contaminant is generated in lowconcentrations and can be controlled to theassigned OEL (see HSE publicationshould consider using LEV to control exposure.EH40/2000 7 ) ; and20 When you use general ventilation to controlthe air flow does not affect the performanceexposure to contaminants generated fromof other extraction systems eg fumeindustrial processes, it is essential that:cupboards, LEV.the rate of contaminant produced is lowenough for it to be effectively diluted bythe airflow rate;Use of recirculated air21 You may want to use recirculated air toconserve energy costs. The extracted airDilutionventilationremoves anyairbornecontaminantswhen lids areremovedLocal exhaustventilation isused tocontrolhazardoussubstancesFigure 4: A factory using a combination of local exhaust ventilation and dilution ventilation to control airborne contaminants5
returned to the workroom can be provided bymechanical ventilation such as an airconditioning system. Conditioning includesSTANDARDS OFGENERAL VENTILATIONheating or cooling the air, filtering it and, in26 The Workplace (Health, Safety and Welfare)some cases, adjusting the humidity to provideRegulations 1992 (WHSW),8 regulation 6the most comfortable working conditionsrequires that you, the employer, do what is(see Figure 5).needed to make sure that every enclosed22 This treatment is unlikely to remove allworkplace is ventilated by a sufficient quantitycontaminants. In some cases they may reachof fresh or purified air.such high concentrations that they cause health27 The Guidance 9 for regulation 6 states thatproblems. This means that you should providethe fresh air supply rate to your workplacean adequate supply of air into the system at ashould not normally fall below 5 to 8 litres persufficient rate to replace lost air. This way yousecond, per occupant. You need to considercan dilute the contaminants using the correctseveral factors when deciding the appropriatefresh air supply rate.rate for your workplace.EmergenciesThese include:23 You must use a risk assessment to decidethe amount of floor space availablehow to manage an emergency. This could be aper occupant;spillage or release of a substance hazardous tohealth, which may be a mist, vapour, gas, fumeor dust, into the atmosphere. Depending onthe level of risk you may then use generalventilation to dilute the air, for instanceopening a window to provide rapid ventilationthe work activity;the smoking habits of the occupants; andwhether there are other sources of airbornecontamination arising from processmachinery, heaters, furniture, furnishings etc.of the environment.24 However, when your employees enter anFactories, hospitals, laboratories etcemergency area for cleaning up they should28 If you use general ventilation to controluse other control measures, for exampleexposure to a substance hazardous to health, itwearing suitable respiratory protectiveis important that you choose the right airequipment to protect them from potentialsupply rate. This should reduce theexposure to hazardous substances.concentrations of the contaminants to well25 If necessary, ventilation systems whichrecirculate air must be switched off to reducethe risk of fire and explosion during theemergency.below the appropriate OELs or to a safe levelwhere OELs are not specified so as to protectyour employees from ill health.29 In this case, it is advisable to consult anoccupational hygienist and/or a ventilation6
Full recirculation(with conditioning)Motorised dampers to controlfresh air intake and exhaustThe use of fresh airand recirculated airFigure 5: Examples of recirculation systems7
e ngineer or other competent person to decideventilation rates can vary considerably for openon the correct ventilation rate and design.flue (drawing air from the room and dischargingproducts outside) and unflued appliancesOffices, shops, theatres etc(drawing air from and discharging products into30 Employees in offices, shops and in thethe room). Further details are given in theentertainment industry are exposed torelevant British Standards (see Furthercontaminants arising from many sourcesInformation).including carpets, furniture, cleaning products,heaters, photocopiers, the building itself, theventilation ducting and from the outsideenvironment.35 Your workers are at risk of gas poisoning,in particular from carbon monoxide, if there isnot enough fresh air in the room to removecombustion products, especially from unflued31 General ventilation is needed to removecombustion equipment. It is essential that allodours, in particular body odours from people,appliances are expertly installed and receiverather than to reduce adverse health effects.regular maintenance and servicing by a32 The recommended fresh air supply ratesper person are given in the CIBSE Guide A:Environmental Design10 produced by thecompetent person.Air movementChartered Institution of Building Services36 Air movement caused by general ventilationEngineers (CIBSE). These are based on dilutingcan affect comfortable working conditions. Yourpersonal odour and cigarette smoke evenworkers will be happier if they can alter theirthough many companies now operate a 'noenvironment, for example by opening or shuttingsmoking' policy or allocate separate smokinga window when required. At normal temperaturesareas.an air flow velocity of between 0.1 to 0.15 metresper second and up to 0.25 metres per second33 A recommended fresh air supply rate ofduring the summer is recommended by CIBSE.108 litres per second per person should provideKeep draughts to a minimum.a clean and hygienic workplace in open planoffices, shops and even factories. Higher freshair supply rates of up to 36 litres per secondper person are recommended for heavilycontaminated buildings ie 70% of peopleHOW TO ACHIEVEEFFECTIVE VENTILATIONIN YOUR WORKPLACEsmoking (see CIBSE Guide A10).37 If your workplace is appropriately designed,Standards for gas, coal or oil firedequipment34 If you use gas, coal or oil fired equipment,the fresh air requirements will d e p e n d on whatkind of flue arrangement you use. Room8for example by providing space for flexibility,and if the building is situated where there isenough shade to minimise summer heat,then you should be able to obtain adequatenatural ventilation.
38 In most buildings make up air (air tokeep doors and windows open to provide areplace that lost from the building) will begood supply of make up air (in winter whensupplied indirectly through gaps around door?the doors and windows are shut, you canand window frames or directly through vents,supply make up air through air vents andwindows, grilles and open doors.extract any contaminated air using asuitable system eg via roof vents);39 But there are things you can do to makeposition fans to extract contaminated airsure you have effective ventilation in yourthrough an extraction point downwind or toworkplace:supply fresh air on a wall and/or in the roof,install trickle ventilators in window framesin particular if your workplace has a largeas well as having windows that open tointernal space (as in many industrial units,provide controllable draught freegarages and warehouses);ventilation (it is important that in winter anywindows are well sealed and secure whenuse fans on the wall of each side of theclosed) (see Figure 6);building to keep fresh air flowingAir containing contaminantsescapes to atmospherevia roof ventsAir enters andescapes throughgaps aroundbuildingOpen windowsFresh air enters viawindows and/or openingsor ventsFigure 6. Natural ventilation moving fresh air through a building9
throughout the building ie one extractingthe contaminated air while the othersupplies fresh air (make sure youremployees work between the air supplyand contaminant source). For example, inmortuaries fresh air should be provided byan inlet located in the ceiling and extractedat a low level outlet to reduce the risk ofmicrobes being inhaled;ASSESSING THEEFFECTIVENESS OFYOUR VENTILATIONSYSTEM43 When required, your initial assessment (seeparagraph 18) should start with information onyour workplace layout, the number of youremployees and their views on the ventilationuse a combination of extraction fans in theprovided, the likely source of pollution,wall and/or roof, with open windows andevidence of draughts, thermal conditions anddoors to supply make up air;the types of ventilation system you are using.discharge any exhausted air above the roofand make sure that there is no opening forsupply air near the exhaust dischargemaking allowance for wind effects; andlocate any exhaust fans as near the sourceof the contamination as possible.Once you have collected this data you can thenassess whether the ventilation systems you useprovide sufficient fresh air.44 Various techniques can be used to assessthe effectiveness of building ventilationsystems ranging from the simple smoke test tothe more complex measurement of tracer gas.40 Situate any extract and supply fan to makesure that there is enough air movement toremove stale and contaminated air from allparts of the room or building. Otherwise youExamples include:using smoke tubes to visualise the patternof air movement in a workplace;may create poorly ventilated areas ormeasuring air velocities either in the'dead zones'.workroom, in ductwork or at grilles to41 You can use portable fans to achieve andetermine air flow rates;adequate air flow at specific sites within ausing tracers to follow air movementbuilding to keep employees cool or tothrough a building or to determine the airremove contaminants generated from aexchange rates by plotting the decay rate ofparticular process.a tracer gas (see HSE publication42 To keep internal conditions constant or tokeep a process clean from airborneMeasurement of air change rales in factoriesand offices11);contaminants you can use a more complexmonitoring airborne contaminants from anmechanical system where the air is recirculatedindustrial process; andafter being filtered.10
measuring carbon dioxide concentrationwhich may contaminate the air and causewithin the workplace; levels over 1,000 ppmhealth problems.may indicate inadequate ventilation (seeCIBSE Guidance Note Healthy Workplaces12).45 Ventilation monitoring using tracers47 As a general rule, if y BS sick building syndrome-.ISBN 0 11 070500 9Guidance for employers, building owners and buildingmanagers HSG 132 HSE Books 199515 The Health and Safety (Consultation withISBN 0 71 76 0861 1Employees) Regulations 1996 SI 1996/1513 HMSO1996 ISBN 0 11 054839 64 Thermal comfort in the workplace HSG 194 HSEBooks 1999 ISBN 0 7176 2468 45 COSHH Essentials: Easy steps to controlchemicals HSG 193 HSE Books 1999ISBN 0 7176 2421 86 Chemicals Hazard Information & Packagingfor Supply (Amendment) Regulations 1997SI 1997/1460 Stationery Office 1997ISBN 0 11 063750 X7 Occupational Exposure Limits Guidance NoteEH40/2000 HSE Books 2000ISBN 0 7176 1315 18 The Workplace (Health, Safety and Welfare)Regulations 1992 SI 1992/3004 HMSO 1992ISBN 0 1 1 025804 59 Workplace health, safety and welfare.Workplace (Health, Safety and Welfare) Regulations1992: Approved Code of Practice and guidance L24HSE Books 1992 ISBN 0 7176 0413 613
FURTHERINFORMATIONHSE publicationsApproved Supply List (5th edition), Informationapproved for the classification and labelling ofsubstances and preparations dangerous for supply.Chemicals (Hazard Information and Packaging forSupply)(Amendment) Regulations 1994(as amended). Approved List. HSE Books 1999ISBN 0 7176 1725 4Safety in the installation and use of gas systemsand appliances. Gas Safety installation and Use)Regulations 1994. Approved Code of Practiceand guidance L56 HSE Books 1994ISBN 0 7176 1635 5Code of practice for ventilation principles and designingfor natural ventilation BS 5925:1991 BritishStandards Institution 1991ISBN 05801 928 57Installation of flues and ventilation for gas appliancesof rated input not exceeding 60 kW(1st, 2nd and 3rd family gases). Part I. Specificationfor installation of flues BS 5440:Part 1: 1990 British Standards Institution 1990ISBN 05801 81421Installation of flues and ventilation for gas appliancesof rated input not exceeding 60 kW(1st, 2nd and 3rd family gases). Part 2. Specificationfor installation of ventilation for gas appliances BS5440: Part 2: 1989 British Standards Institution1989 ISBN 05801 80050Maintenance, examination and testing of local exhaustOther publicationsventilation 2nd edition HSG54 HSE Books 1998CIBSE Guide: Volume B: Installation andISBN 0 7176 1485 9equipment data 5th edition CIBSE 1986Ventilation of kitchens in catering establishments HSEISBN 0 900953 30 6Information Sheet: Catering Sheet No 10 HSECIBSE Guide: Volume C: Reference dataBooks 19975th edition CIBSE 1986 ISBN 0 90053 31 4The control of legionellosis including legionnairesCIBSE Hygiene maintenance of office ventilationdisease 2nd edition HSG70 HSE Books 1993ductwork TM26:1999 CIBSE 2000ISBN 0 7176 0451 9(to be published later this year)An introduction to local exhaust ventilation HSG37The Building Regulations 1991. Fl Means ofHMSO 1993 ISBN 0 11 882134 2ventilation. F2 Condensation in roofs HMSO 1994Passive smoking at work: Workplace air pollutionISBN 0 11 752932 XINDG63REV HMSO 1992CIBSE Minimising pollution at air intakes - TM21:British Standards Institutionpublications1999 CISBE 1999 ISBN 0900 953 91 8Code of practice for mechanical ventilation and airconditioning in buildings BS 5720:1979 BritishStandards Institution 1979 ISBN 05801 071 8314CIBSE Natural ventilation in non-domestic buildings- Applications Manual AM 10: 1997 CIBSE1997 ISBN 0 000953 77 2
American Society of Heating, RefrigeratingBritish Standards are available from BS1and Air-conditioning Engineers Inc VentilationCustomer Services, 389 Chiswick High Road,for acceptable indoor air quality ASHRAE StandardLondon W4 4AL. Tel: 020 8996 9001.62-1989 ASHRAE 1989Fax: 020 8996 7001.ISSN 1041 2336The Chartered Institution of Building ServicesTR/17 Guide to good practice - Cleanliness ofEngineers (CIBSE), tel: 020 8675 5211ventilation systems Heating and Ventilatingpublishes various technical guides onContractors'Association 1998building design and general ventilation forISBN 0 9037 83 26 6example the applications manual NaturalThe American Conference of Governmentalventilation in non-domestic buildings (see above)Industrial Hygienists Induslrial ventilation.which provides guidance on how to ensureA manual of recommended practice. 23rd Editionnatural ventilation, standards etc.(Metric Version) 1998 1 SBN 1 882417 26 7The Building Services Research andWhile every effort has been made to ensureInformation Association (BSRIAI,the accuracy of the references listed in thistel: 01344 426511 publishes technicalpublication, their future availability cannotdocuments on general ventilation andbe guaranteed.provides information.Useful organisationsThe following organisations produce generalinformation, guides, and standards ongeneral ventilation:The Building Research Establishment (BRE),tel: 01923 894040 publishes technicalguidance on general ventilation.The American Society of Heating,Refrigerating and Air-conditioning EngineersThe Heating and Ventilating ContractorsInc (ASHRAE) can be contacted onAssociation (HVCA), tel: 020 7229 2488tel: 001 404 636 8400.publishes guidance on testing andmaintenance.The British Occupational Hygiene Society(BOHS), tel: 01332 298101 has produced ageneral guide on controlling hazardoussubstances in the workplace, Technical GuideNo 7: Controlling airborne contaminants inthe workplace.The British Institute of OccupationalHygienists (BIOH) tel: 01332 298087 provideinformation on occupational hygiene,including general ventilation.15
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Fresh air supply fan in wall filtered to remove particulates, and should have fresh air added to it before being reintroduced into the workplace. 9 When providing fresh air for your employees, make sure there are no uncomfortable draughts from the movement of air. Health effects of insufficient fresh air 1
Mechanical Ventilation: Schedule History, Concepts and Basic Physiology – Nader Volume Control Ventilation (CMV, ACV) – Nader Intermittent Mandatory Ventilation (SIMV) – Nader Pressure Support Ventilation (PSV) – Nader Pressure Control Ventilation (PCV) –
ventilation à haute fréquence aboutirent à la mise au point de deux types très différents d'appareils : ceux délivrant la ventilation par percussions à haute fréquence ou high frequency percussive ventilation (HFPV) et ceux délivrant la ventilation à percussions intrapulmonaires ou intra-pulmonary percussive ventilation (IPV).
Mechanical Ventilation: Schedule History, Concepts and Basic Physiology - Nader Volume Control Ventilation (CMV, ACV) - Nader Intermittent Mandatory Ventilation (SIMV) - Nader Pressure Support Ventilation (PSV) - Nader Pressure Control Ventilation (PCV) - Junker Pressure Regulated Volume Control (PRVC) - Junker
Ventilation Guide www.xpelair.com. . heating and ventilation products nationally and internationally. With over 55 years of ventilation expertise, Xpelair has earned an enviable reputation in world class domestic, commercial and industrial ventilation, leading the way with innovative technologies and style to ensure the air we breathe is
With “Basic Assessment and Support in Intensive Care” by Gomersall et all as a foundation, I built using the humongous ndand canonical “Principles and Practice of Mechanical Ventilation” by Tobins et al – the 1442 page 2 edition CMV: Continuous Mandatory Ventilation VOLUME CONTROLLED CMVFile Size: 309KBPage Count: 9Explore furtherContinuous Mandatory Ventilation - an overview .www.sciencedirect.comSynchronized Intermittent Mandatory Ventilationpubmed.ncbi.nlm.nih.govContinuous mandatory ventilation - Wikipediaen.wikipedia.orgRecommended to you b
(10) A mode of ventilation is classified according to its control variable, breath sequence, and targeting schemes. CMV continuous mandatory ventilation IMV intermittent mandatory ventilation CSV continuous spontaneous ventilation VC volume control PC pressure control TAXONOMY FOR MECHANICAL
Alternative ventilation types Mouthpiece “sip” ventilation Biphasic cuirass ventilation Invasive ventilation Rates of tracheostomy placement for ventilation vary by disease state and prognosis E.g. Duchenne MD vs. ALS Special consider
1.1 The HRV AirSense Ventilation System is a roof space mounted, ducted, ventilation system for houses. Scope 2.1 The HRV AirSense Ventilation System is a mechanical positive air-handling and ventilation system predominantly for existing detached housing where buildings show signs of condensation and air quality problems.
