Engineering ToolBox - Resources, Tools and Basic Information for Engineering and Design of Technical Applications!

Air Supply to a Boiler House

Incomplete boiler combustion may generate carbon monoxide - CO - and re-ignition may cause disastrous effects on personnel and property.

For proper combustion and safety precautions it is necessary to provide boiler rooms with appropriate openings for fresh air supply. Temporary air intakes - such as windows and doors - should be avoided since they may be closed (and often they are when persons in the boiler room feel the cold) and cutting off the boiler's air supply.

If combustion air supply is limited the fire starts to smoke, incomplete combustion occur and carbon monoxide is generated. If the fire goes out before the flame detection system acts to close the fuel safety shutoff valve, accumulated fuel may re-ignite when oxygen seeps in through cracks and crevices. A furnace explosion may occur with disastrous effects on personnel and property.

  • adequate air supply is required to minimize the possibility of an explosion

Codes addressing the amount of combustion air or size of the opening in the walls for combustion air in the boiler room:

  • ASME CSD-1- Controls and Safety Devices for Automatically Fired Boilers, 1992 with addendum 1a 1993. section CG-260 Combustion Air.
  • ASME Section VI Recommended Rules for the Care and Operations of Heating Boilers.
  • NFPA 54 - National Fuel Gas Code, 1992, section 5.3 Air for Combustion and Ventilation.
  • NFPA 31 - Installation of Oil Burning Equipment, 1992, section 1-5 Air for Combustion and Ventilation.
  • BOCA - National Mechanical Code, 1990, article 10, Combustion Air.
  • SBCCI- Standard Mechanical Code, 1991, section 305 Combustion and Ventilation Air.
  • American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Handbook - Fundamentals, 1993, Chapter 15, page 15.9 Air For Combustion.

ASME CSD-1- Controls and Safety Devices for Automatically Fired Boilers, 1992 with addendum 1a 1993. section CG-260 Combustion Air

Sections covers the requirements for combustion air intakes.

The American Society of Mechanical Engineers, ASME

ASME Section VI Recommended Rules for the Care and Operations of Heating Boilers

Reference 6.04 states:

The boiler room must have adequate air supply to permit clean, safe combustion and to minimize soot formation. An unobstructed air opening should be provided. It may be sized on the basis of 1-square inch free area per 2000-btu/hr maximum fuel input of combined burners located in the boiler room, or as specified in the National Fire Protection Association standards for oil and gas burner installations for the particular job conditions. The boiler room air supply openings must be kept clear at all times.

From experience the ASME rule of 1-square inch free area per 2000-btu/hr (Unit Converter) maximum fuel input of combined burners located in the boiler room works. I general rounded up to the next common size.

NFPA 54 - National Fuel Gas Code, 1992, section 5.3 Air for Combustion and Ventilation

provides requirements for installation and operation of gas piping, equipment installations and venting. It is the accepted national measure for all fuel gas installations.

Gas Fuels

Minimum No. openings required 2
Outdoor opening (sq. in./Btu h) 1/4000
Vertical ducts (sq. in./Btu h) 1/4000
Horizontal ducts (sq. in./Btu h) 1/2000
Ducts same as opening yes
Minimum duct dimension  (inches) 3
Louver & grill free area opening
Free area allowance, wood* 20-25%
Free area allowance, metal* 60-75%
Damper interlocked yes

* It is assumed that wood louvers and grilles have 20-25% free area. Metal louvers and grilles 60-75% respectively.

NFPA 31 - Installation of Oil Burning Equipment, 1992, section 1-5 Air for Combustion and Ventilation

Covers minimum requirements for safety to life and property from fire in the installation of oil burners and the equipment used in connection with them.

Oil Fuels

Minimum No. openings required 2
Outdoor opening (sq. in./Btu h) 1/4000
Vertical ducts (sq. in./Btu h) 1/4000
Horizontal ducts (sq. in./Btu h) 1/2000
Ducts same as opening yes
Minimum duct dimension (inches) 3
Louver & grill free area opening
Free area allowance, wood* 20-25%
Free area allowance, metal* 60-75%

BOCA - National Mechanical Code, 1990, article 10, Combustion Air

All Fuels

Minimum No. openings required 2
Outdoor opening (sq. in./Btu h) 1/4000
Vertical ducts (sq. in./Btu h) 1/4000
Horizontal ducts (sq. in./Btu h) 1/2000
Minimum duct dimension (inches) 3
Free area allowance, wood 25%
Free area allowance, metal 75%
Damper interlocked yes

SBCCI- Standard Mechanical Code, 1991, section 305 Combustion and Ventilation Air.

Gas and Oil Fuels

Minimum No. openings required 2
Outdoor opening  (sq. in./Btu h) 1/4000
Vertical ducts (sq. in./Btu h) 1/4000
Horizontal ducts (sq. in./Btu h) 1/2000
Ducts same as opening yes
Minimum duct dimension (inches) 3

Solid fuels

Minimum No. openings required 2
Outdoor opening  (sq. in./Btu h) 2/1000
Minimum duct dimension  (inches) 3
Louver & grill free area opening

American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Handbook - Fundamentals, 1993, Chapter 15, page 15.9 Air For Combustion

Related Topics

  • Combustion

    Combustion processes and their efficiency. Boiler house and chimney topics. Properties of fuels like oil, gas, coal and wood and more. Safety valves and tanks.

Related Documents

Search

Search is the most efficient way to navigate the Engineering ToolBox.

Engineering ToolBox - SketchUp Extension - Online 3D modeling!

3D Engineering ToolBox Extension to SketchUp - add parametric components to your SketchUp model

Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your Sketchup model with the Engineering ToolBox - SketchUp Extension - enabled for use with older versions of the amazing SketchUp Make and the newer "up to date" SketchUp Pro . Add the Engineering ToolBox extension to your SketchUp Make/Pro from the Extension Warehouse !

Translate this Page

Translate this page to Your Own Language .

About the Engineering ToolBox!

Privacy Policy

We don't collect information from our users. More about

We use a third-party to provide monetization technologies for our site. You can review their privacy and cookie policy here.

You can change your privacy settings by clicking the following button: .

Citation

This page can be cited as

  • The Engineering ToolBox (2003). Air Supply to a Boiler House. [online] Available at: https://www.engineeringtoolbox.com/supply-air-boiler-room-d_174.html [Accessed Day Month Year].

Modify the access date according your visit.

3D Engineering ToolBox - draw and model technical applications! 2D Engineering ToolBox - create and share online diagram drawing templates! Engineering ToolBox Apps - mobile online and offline engineering applications!

Unit Converter

















































11.4.12

.