Homeowners Guide to Chimney Inspections and Cleaning
A chimney is a building structure manufactured or constructed to enclose one or more vertical passages, called flues, where the products of combustion pass safely outside the structure. The flue is the working part of the chimney and can be comprised of a pipe or shaft for the passage of smoke, hot air and gas in a chimney. Chimneys are exposed to extremes in temperature, ice, snow, and rain as well as animals that attempt to take advantage of the heat and shelter to build nests. Malfunctioning appliances or improper fireplace use can prematurely age a flue and chimney and create a situation where water or fire damage can occur or dangerous levels of carbon monoxide can enter a home and result in the death of building occupants.
A masonry chimney needs to have a sound foundation to prevent movement and prevents the leakage of combustion gases and prevent setting the building on fire. Zero-clearance chimneys are constructed of multiple, concentric cylinders of sheet metal with air space in between each layer to lower the temperature of the outer surface of the chimney and can come in contact with building materials.
A related component is a vent connector or flue vent connector. A vent is a product intended to serve a specific type of appliance under narrowly defined conditions. For example, the thin-walled metal pipe, typically 6" in diameter or larger and used to connect an oil-fired heating boiler or a gas-fired furnace to a metal or masonry chimney is properly called the flue vent connector. They are often referred to as "flue pipe" or "stack pipe". There are important safety regulations about these components, installation, fire clearances, and fire ratings of flue vent connectors and their component parts which are not covered in this article.
Types of Chimney Inspections
On January 13, 2000, the National Fire Protection Association (NFPA) adopted these levels of inspection into code NFPA 211 (Standard for Chimneys, Fireplaces, Vents and Solid Fuel Burning Appliances) and the inspections are now clearly defined as Level 1, Level 2 or Level 3 .
NFPA 211 is the standard upon which certified chimney sweeps base their services and Chimney Safety Institute of America (CSIA) Certified Chimney Sweeps are tested to these three levels of inspection. Each level of inspection covers specific items depending on the individual appliance and venting system.
Level 1 inspections –
A Level 1 inspection is recommended for a chimney under continued service, under the same conditions, and with the continued use of the same appliance. In a Level 1 inspection, your chimney service technician should examine the readily accessible portions of the chimney exterior, interior and accessible portions of the appliance and the chimney connection. The basic soundness of the chimney structure and flue as well as the basic appliance installation and connections will be inspected. The chimney flue is also checked to verify that it is free of obstruction and combustible deposits.
Level 2 Inspections –
A Level 2 inspection is required when any changes are made to the system. Changes can include a change in the fuel type, changes to the shape of, or material in, the flue such as when flues are relined, or the replacement or addition of an appliance of a dissimilar type, input rating or efficiency. Additionally, a Level 2 inspection is required upon the sale or transfer of a property or after a malfunction or external event that is likely to have caused damage to the chimney. Building fires, chimney fires, seismic events as well as weather events are all indicators a Level 2 inspection is needed. A Level 2 inspection is a more in-depth inspection than a Level 1 inspection. When a Level 1 or Level 2 inspection suggests a hidden hazard and the evaluation cannot be performed without special tools to access concealed areas of the chimney or flue, a Level 3 inspection is recommended. A Level 2 inspection includes everything in a Level 1 inspection, plus the accessible portions of the chimney exterior and interior including attics, crawl spaces and basements. It will address proper clearances from combustibles in accessible locations.
There are no specialty tools required to open doors, panels or coverings in performing a Level 2 inspection. A Level 2 inspection shall also include a visual inspection by video scanning or other means in order to examine the internal surfaces and joints of all flue liners incorporated within the chimney. No removal or destruction of permanently attached portions of the chimney or building structure or finish shall be required by a Level 2 inspection.
Level 3 Inspections -
A Level 3 inspection includes all the areas and items checked in a Level 1 and a Level 2 inspection, as well as the removal of certain components of the building or chimney where necessary. Removal of components (i.e., chimney crown, interior chimney wall) shall be required only when necessary to gain access to areas that are the subject of the inspection. When serious hazards are suspected, a Level 3 inspection may well be required to determine the condition of the chimney system. Some demolition may be necessary to access the chimney components in a Level 3 inspection.
The results of a chimney inspection should be presented to you in written form. Most sweeps have a special form for this purpose. In addition to performing a visual inspection, many sweeps have a video camera which is lowered into the chimney for a more detailed, close-up look at the chimney interior. This method can also produce photos or a video tape for more complete documentation. If you are interested in this service, be sure to request it, as this is generally not included in a routine inspection.
Whenever possible, have chimney inspections performed by "CSIA Certified Chimney Sweeps". The Chimney Safety Institute of America sponsors a certification program for chimney sweeps. For a list of "CSIA Certified Chimney Sweeps" in your area visit their website at http://www.csia.org/ or write the Chimney Safety Institute of America at 2155 Commercial Drive, Plainfield, IN 46168.
Look for this mark whenever you hire a chimney sweep.
Changes in Use
NFPA 54, the National Fuel Gas Code, recommends that when a new appliance is retrofitted into an existing installation, or an existing appliance is removed from a common vent, the entire venting system, which may include a masonry chimney, should conform to current codes.
Many houses inspected have had higher efficiency appliances installed, some that are direct vented, and it has been observed that corrosion can occur at vent connector pipes, chimney cleanout doors and disintegrated masonry at the cleanout.
Chimneys can be constructed in three main ways, inside, outside, and three-sided.
All chimneys whose construction is entirely internal to the building structure up to the roof line are considered inside chimneys.
Chimneys with three walls exposed to the outdoors are considered outside chimneys. Vents may experience continued condensation.
Three Sided Chimneys
A three-sided is one which does not provide full masonry thickness or fire protection around all sides of the chimney flue. Three sided chimneys pose a serious fire risk because the chimney has been built close to or even directly against combustible building materials without the necessary fire clearance and masonry fire protection needed.
Chimney deposits can be dangerous as they are a fuel source that can be burning if flue temperatures are elevated or embers come in contact with the deposits. There are several forms of deposits, but there are three basic types.
Soot - Soot is primarily composed of carbon particles but may also contain ash. Soot has a soft texture and will be black or brown in color. The flammability of soot will depend on the concentration of soot and ash. Soot is combustible while ash is noncombustible.
Creosote - Creosote can be defined as a combustible deposit in the venting system which begins as condensed wood smoke including tar vapors. Creosote is a by-product of incomplete combustion. Creosote will be hard brown or black and form either curly, flaky deposits or bulbous deposits in the venting system. Creosote is flammable.
Glaze - Glaze is a form of deposit that is a shiny tar-like substance. Glaze can form puddles or drop down and make formations that resemble black icicles. Glaze is the most dense type of wood burning deposit and, therefore, represents the greatest amount of fuel to burn in the event of a chimney fire. Glaze is also the most difficult type of deposit to remove from the chimney.
Removal of Deposits
Standard Cleaning - Standard cleaning involves the use of brushes to clean the flue walls. A powerful vacuum connected to the bottom of the flue to prevent soot and creosote from entering the home. This type of cleaning is effective for soot and ordinary creosote deposits but has little effect on glaze deposits.
Mechanical Cleaning - Mechanical cleaning involves the use of wire brushes, plastic cables or special chains rotated at high speed by an electric motor. Mechanical cleaning is often employed to remove hard creosote or glaze deposits. Mechanical cleaning should only be attempted by professional sweeps familiar with the use of this type of equipment. The improper use of mechanical cleaning tools can damage the chimney.
Chemical cleaning - Some sweeps prefer to use chemical cleaning combined with mechanical cleaning or just chemical cleaning. Special chemicals are used to loosen or dissolve heavy deposits of creosote and glaze. Chemical cleaning should only be attempted by trained professional sweeps.
Masonry and Zero-Clearance Chimney Construction
Masonry Chimney Detail
Prefab or Zero-Clearance Chimney Detail
Chimney caps are an important and necessary component on a chimney flue. Caps prevent water from running into the chimney where the water seeps into the bricks and mortar, settling behind the firebricks in the fireplace. Since there is little to no air circulation in the chimney, except when it is in use, and no sunlight, the inside of the chimney stays wet long after the rain stops. This moisture erodes the mortar joints and weakens the brick. The freeze/thaw cycle during winter months accelerate the deterioration of the chimney.
Besides keeping the rain out, chimney caps also keep out animals and birds, keep out leaves, twigs and other debris which could lead to a blockage or chimney fire, keep sparks from exiting the chimney and igniting nearby combustibles., and helps eliminate wind induced downdrafts.
Chimney caps are made from a variety of materials. The most common are galvanized, stainless steel, and copper. Caps made of stainless steel and copper will last much longer than those made of regular galvanized steel and they normally carry an extended warranty.
Rules for Fireplace and Chimney Design
While there are many factors which affect fireplace performance, you may want to check your fireplace and chimney to determine if they are close to these rules:
Ratio of Fireplace Opening to Chimney Flue Size: The area of the flue should be roughly one-twelfth (1/12) the size of the opening area.
Chimney Height: At least 3 feet above the roof and 2 feet higher than anything within 10 feet of it. Wood burning stoves with metal flues have different requirements so you should check with the unit manufacturer but most require a minimum length of 15 feet.
Damper Size and Location: Full width of firebox and at least 6 inches above the top of the opening. The damper is usually closer to the front of the fireplace than the back.
Smoke Chamber Slope and Smoothness: The chamber above the damper should be as smooth as possible, and should slope no more than 45 degrees.
National Fire Protection Association
Chimney Safety Institute of America