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APPENDIX A
INSIDE COMBUSTION AIR CONTAMINATION:
All boilers experience some condensation during start-up.
The condensate from flue gas is slightly acidic. In most cases the pH level is not harmful to vents or drains. When
combustion air is contaminated by vapors from products in areas listed below, the acidic levels in the condensate increase.
Higher acidic levels attack many materials, including stainless steel commonly used in high efficiency systems.
The boiler can use special corrosion-resistant nonmetallic intake vent material. You may, however, choose to use outside
combustion air for one or more of these reasons:
• installation is in an area containing contaminants listed below which will induce acidic condensation.
• you want to reduce infiltration into your building through openings around windows and doors.
• you are using AL29-4C stainless steel vent pipe, which is more corrosion-resistant than standard metallic vent
pipe. In extremely contaminated area, this may also experience deterioration.
Products causing contaminated combustion air:
• spray cans containing chloro/fluorocarbons
• permanent wave solutions
• chlorinated waxes/cleaners
• chlorine-based swimming pool chemicals
• calcium chloride used for thawing
• sodium chloride used for water softening
• refrigerant leaks
• paint or varnish removers
• hydrochloric acid/muriatic acid
• cements and glues
• antistatic fabric softeners used in clothes dryers
• chloride-type bleaches, detergents, and cleaning solvents found in household laundry rooms
• adhesives used to fasten building products
• ... and other similar products.
Areas causing contaminated combustion air:
• dry cleaning/laundry areas and establishments
• metal fabrication plants
• beauty shops
• refrigeration repair shops
• photo processing plants
• auto body shops
• plastic manufacturing plants
• furniture refinishing areas and establishments
• new building construction
• remodeling areas.
Check for areas and products as listed above before installing boiler. If found:
• remove products permanently, OR
• provide outdoor combustion air.
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