The Need for Make-up Air

Air exhausted from industrial or commercial buildings must be replaced. If provisions are not made for make -up air, there likely will be air starvation creating negative pressure within the building . This negative pressure, in turn, causes: outside air infiltration and cold drafts; down or back drafts in heating equipment flues,ventilators and stacks;reduced exhaust fan air volumes resulting in inadequate removal of contaminants; uncomfortable, and in many instances, unhealthy working conditions; and other problems.

The Source of Make-Up Air

With most applications requiring exhaust air provisions, replacement air must enter buildings either by infiltration through openings such as doors or windows, or supplied by a make -up air system. Infiltrated air is unheated, draft ridden and unfiltered resulting in an uncomfortable, uneven, and often unclean environment. A controlled source of make -up air eliminates the many problems of infiltration.

The SBD Direct Gas - Fired Systems

The SBD series of direct  gas - fired make -up air system was designed to furnish fresh, clean and heated air from a controlled source by the most fuel efficient and cost effect means. The SBD system employ a method of supplying heated air into a building by passing fresh air directly over a gas flame in the air stream. The burner utilizes the kinetic energy of the air flow to complete combustion with the products of combustion well within code prescribed safely limits. The direct gas- fired burner, depicted in Figure 1. consists of drilled port cast iron pipe and two perforated stainless steel combustion baffles. The arrangement and shape of the air hole in the bafflies provide the injection of proper combustion air at all rates of firing over a wide turndown range of up to 25:1. Since all the heat of the fuel goes into the  air stream being heated, the direct gas- fired unit has 100% combustion efficiency and 92% overall thermal efficiency (with 8% of the total heat lost in the latent heat of water formed in combustion)

HOW CAN YOU RECOGNIZE
THE NEED FOR MAKE -UP AIR?

Symptoms:

     Back drafts and frequent pilot outages on natural draft heating equipment

     Doors difficult to open

     Exhaust fans not exhausting air

Cause:

    Negative inside pressure from too little air replacing the air being exhausted

Symptoms:

      Heaters not heating buildings

      Cold drafts

      Dust and dirt being drawn into building

Cause:

      Untreated outside air infiltrated into building because of negative inside pressure

Symptoms:

     Employees develop nausea and headaches

Cause:

    Build-up of inside contaminants due to inadequate ventilation

Figure1