Upper and lower openings|3M Construction Assembling & Trading Co., Ltd
3M Construction Assembling & Trading Co., Ltd


  • Tiếng Anh
  • Tiếng Việt
+84 903 815 852 - +84 225 3 564 259

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119/81 Nguyen Trai street, Ngo Quyen district, Hai Phong city, Vietnam

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Upper and lower openings

Views: 215

These are  required  by  regulations  and  good practices. They must  be clear and unobstructed.

Surface of openings:

To determine   the surface   area  of  openings, experience   dictates   the  use  of a ratio of

1/23rd  of total  installed  power.

Example: lnstalled  power  70  kw

Surface  area  of  upper  opening  and  lower  opening:

70:23  = 3,04dm2  , that is 304 cm2

For  small  installations: see DTU and  good  practices Example  of a  butane  cylinder  supplying a gas  cooker : Openings are  100  cm2 each

Example  of a  butane  cylinder  supplying a gas  cooker and a water heater: Openings are  150  cm2 each.


To  burn 1kg of butane , 33 m3 of air  is needed. To  burn 1kg of propane , 26 m3 of air  is needed.

If the combustion  lacks  air , CO2  and CO  is  produced.  To  avoid  an  incident  occurring or  asphyxia ,  openings should  be  properly  dimensionned.