Ip10b

Continuous particulate monitor

Source: W. T. Winberry et al., "EPA Project Summary Compendium of Methods for the Determination of Air Pollutants in Indoor Air," EPA/600/S4-90/010, U.S. Environmental Protection Agency, Atmospheric Research and Exposure Assessment Laboratory, Research Triangle Park, NC, May 1990.

Source: W. T. Winberry et al., "EPA Project Summary Compendium of Methods for the Determination of Air Pollutants in Indoor Air," EPA/600/S4-90/010, U.S. Environmental Protection Agency, Atmospheric Research and Exposure Assessment Laboratory, Research Triangle Park, NC, May 1990.

systems are very effective for the removal of dust and other particulates without resuspending the finer particles indoors.

Venting of Heating Units

Proper venting is the removal of all the products of combustion through a designated channel or flue to the outside air with maximum efficiency and safety.

Gravity-type venting relies largely on having the vent gases inside the vent hotter (thus lighter) than the surrounding air. The hotter the vent gases, the lighter they are and the greater their movement up through the vent. Thus, in order to keep the vent gases hot so that they may work at maximum efficiency, proper installation and insulation are necessary.

Factors that prevent proper venting are abrupt turns; downhill runs; common vents to small, uninsulated vent pipes; conditions that cause backdrafts; obstructions in the flue or chimney to which a furnace, heater, or stove is connected such as birds nests, soot and debris, broken mortar and chimney lining, and old rags; and unlined masonry chimneys. Stained and loose paper or falling plaster around a chimney is due to poor construction. A masonry chimney will absorb a great deal of the heat given off by the vent gases, thus causing the temperature in the chimney to fall below the dew point. The high moisture in vent gases condenses inside the chimney, forming sulfuric acid. This acid attacks the lime in the mortar, leaching it out and creating leaks and eventual destruction of the chimney. Therefore, it is necessary to line a masonry chimney with an insulating pipe, preferably terracotta flue lining.

Figure 2.16 shows chimney conditions apt to result in backdrafts. The flue or vent should extend high enough above the building or other neighboring obstructions so that the wind from any direction will not strike the flue or vent from an angle above the horizontal. Unless the obstruction is within 30 feet or is unusually large, a flue or vent extended at least 3 feet above flat roofs or 2 feet above the highest part of wall parapets and peaked roof ridges will be reasonably free from downdrafts.

To ensure proper venting as well as proper combustion, sufficient amounts of fresh air are required, as shown in Figure 2.16. An opening of 100 to 200 in.2 will usually provide sufficient fresh air under ordinary household conditions; this opening is needed to float the flue gases upward and ensure proper combustion in the fire box. Proper venting and an adequate supply of fresh air are also necessary for the prevention of carbon monoxide poisoning or asphyxiation.

The connection (breeching) between the furnace or stove and chimney should be tight fitting and slope up to the chimney at least 1/4in./ft. Chimneys are usually constructed of masonry with a clay tile flue liner or of prefabricated metal with concentric walls with air space or insulation in between and should be Underwriter's Laboratories approved. All furnaces and stoves should be equipped with a draft hood, either in the breeching or built into the furnace or stove, as required, for proper draft. See Figure 2.16.

Before making any vent installations or installing any gas- or oil-fired appliances, consult the building code and the local gas or utility company. Standards for chimneys, fireplaces, and venting systems, including heating appliances and incinerators, are given by the National Fire Protection Association,60 building codes, and other publications.

Portable kerosene heaters are a fire hazard and, since they are not vented, emit dangerous gases into a room. Their sale and use should be prohibited. The

FIGURE 2.16 Some venting details. (Drawings are typical and not necessarily in full accordance with any code.) See state and local building and fire prevention codes.

concentrations of carbon dioxide, nitrogen dioxide, and sulfur dioxide emitted into a room usually greatly exceed ambient air standards.

Wood stoves require special fire protection and venting. See Cooperative Extension Service recommendations and local building code requirements.

Chimneys, vents, and ducts can become blocked by bird nests, squirrel nests, soot, grease, leaves, and other debris. Such conditions can develop during the nonheating season, which will prevent proper venting of the heating unit. Dangerous levels of carbon monoxide can accumulate if chimneys, vents, and ducts are not kept clear.

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