ISO INTERNATIONAL STANDARD 21927-4 First edition 2019-04 Smoke and heat control systems - Part 4: Natural smoke and heat exhaust ventilators - Design, requirements and installation Systemes pour le controle des fumées et de la chaleur - Partie 4: Exutoires de fumées et de chaleur naturels - Dimensionnement, exigences et mise en place Reference number ISO 21927-4:2019(E) osi @ IS0 2019 IS0 21927-4:2019(E) COPYRIGHTPROTECTEDDOCUMENT @ IS0 2019 All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either IsO at the address below or Iso's member body in the country of the requester. ISO copyright office CP 401 : Ch. de Blandonnet 8 CH-1214 Vernier, Geneva Phone: +41 22 749 01 11 Fax: +41 22 749 09 47 Email: copyright@iso.org Website: www.iso.org Published in Switzerland ii @ IS0 2019 - All rights reserved IS0 21927-4:2019(E) Contents Page Foreword ..iv Introduction. ..V 1 Scope. ..1 2 Normative references 3 Terms and definitions 4 Symbols and abbreviated terms. ..2 5 Design principles .2 5.1 General. .2 5.2 Height of space .3 5.3 Target height of the clear layer, height of smoke barrier .3 5.4 Area of smoke reservoir .4 5.5 Air inlets. .4 5.6 Duration of fire growth ..5 5.7 Theoretical fire area, design groups .5 5.8 Aerodynamic effectiveness of NSHEVs .6 6 Design ..6 6.1 General .6 6.2 Smoke exhaust openings in roofs ..6 6.3 Smoke exhaust openings in walls .12 7 Installation ..13 7.1 General ..13 7.2 Rules for installation ..13 8 NSHEVs combined with fire extinguishing equipment ..14 9 Testing, maintenance and repair .15 9.1 Testing ..15 9.2 Maintenance ..15 9.3 Repair. .15 Bibliography ..16 @ IS0 2019 - All rights reserved ii