GSA
Gas-Fired Steam Boilers –
Boiler Manual
5
Part Number 550-110-738/1012
Figure 2
Terminations with Type B
vent fitted with
listed cap,
provided vent is at least 8 feet from
any vertic
al
wall or similar obstruction locations
1 Prepare boiler location
continued
Air contamination
Please review the following information on potential combustion
air contamination problems.
See Table 2 for products and areas which may cause contaminated
combustion air.
To prevent potential of severe personal injury or
death, check for products or areas listed below
before installing boiler. If any of these contaminants
are found:
• Remove contaminants permanently.
— OR —
• Isolate boiler and provide outside combustion
air. See national, provincial or local codes for
further information.
Table 2
Corrosive contaminants and likely locations
Vent System
Chimney or vent requirements
1. Venting must be installed according to the National Fuel Gas
Code, ANSI Z223.1–latest edition and applicable building
codes. Canadian installations must comply with B149.1 or
B149.2 Installation Codes.
2. See “Ratings” on page 31 for minimum chimney or vent sizes.
Chimney or vent termination:
• A chimney, or any vent other than a Type B vent with listed
vent cap, must extend at least 3 feet above the highest
point where it passes through a roof of a building, and at
least 2 feet higher than any portion of a building within a
horizontal distance of 10 feet.
• Type B vents with listed caps may terminate as in Figure 2
if no closer than 8 feet from a vertical wall or similar
obstruction.
• Otherwise, Type B vents must terminate at least 2 feet
above the roof penetration and at least 2 feet higher than
any portion of a building within 10 feet.
3. A lined chimney is preferred and must be used when required
by local, state, provincial and national codes, laws, regulations
and ordinances. Vitreous tile linings with joints that prevent
retention of moisture and linings made of noncorrosive
materials are best. Advice for flue connections and chimney
linings can be obtained from local gas utility. Type B double‑
wall metal vent pipe or single-wall vent pipe may be used as
a liner.
4. Cold masonry chimneys, also known as outside chimneys,
typically have one or more walls exposed to outside air.
When any atmospheric gas-fired boiler with automatic vent
damper is vented through this type of chimney, the potential
exists for condensation to occur. Condensation can damage a
masonry chimney. The following are recommended to prevent
possible damage.
a. Line chimney with corrosion-resistant metal liner such as
AL29‑4C® single‑wall stainless steel or B‑vent. Size liner
per National Fuel Gas Code ANSI Z223.1–latest edition.
b. Provide drain trap to remove any condensate.
5. Where two or more gas appliances vent into a common
chimney or vent, equivalent area should be at least equal to
area of vent outlet on largest appliance plus 50 percent of vent
outlet area of additional appliances.
Products to avoid
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
Chlorine-type bleaches, detergents, and cleaning solvents found in
household laundry rooms
Adhesives used to fasten building products and other similar
products
Areas likely to have contaminants
Dry cleaning/laundry areas and establishments
Swimming pools
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
Garages with workshops
Buildings under construction (where air is contaminated with
particulates)
