A smoke alarm, also known as a smoke detector, is a device that detects smoke and issues an audible sound and/or a visual signal to alert residents to a potential fire.
Facts and Figures

Smoke Alarm Types
Ionization and photoelectric are the two main designs of smoke detectors. Both types must pass the same tests to be certified to the voluntary standard for smoke alarms, but they perform differently in different types of fires. Detectors may be equipped with one or both types of sensors -- known as dual-sensor smoke alarms -- and possibly a heat detector, as well. These sensors are described as follows:

• Ionization smoke sensors are the most common and economical design, and are available at most hardware stores. They house a chamber sided by small metal plates that irradiate the air so that it conducts electricity. When smoke enters the chamber, the current flow becomes interrupted, which triggers an alarm to sound. These sensors will quickly detect flaming-type fires but may be slower to react to smoldering fires.
• Photoelectric smoke sensors use a light-sensitive photocell to detect smoke inside the detector. They shine a beam of light that will be reflected by smoke toward the photocell, triggering the alarm. These sensor types work best on smoldering fires but react more slowly to flaming fires. They often must be hard-wired into the house's electrical system, so some models can be installed only in particular locations.

While heat detectors are not technically classified as smoke detectors, they are useful in certain situations where smoke alarms are likely to sound false alarms. Dirty, dusty industrial environments, as well as the area surrounding cooking appliances, are a few places where false alarms are more likely and where heat detectors may be more useful.
Location
Individual authorities having jurisdiction (AHJs) may have their own requirements for smoke-alarm placement, so inspectors and homeowners can check with their local building codes if they need specific instructions. The following guidelines, however, can be helpful.
Smoke alarms should be installed in the following locations:

• on the ceiling or wall outside of each separate sleeping area in the vicinity of bedrooms;
• in each bedroom, as most fires occur during sleeping hours;
• in the basement, preferably on the ceiling near the basement stairs;
• in the garage, due to all the combustible materials commonly stored there; 
• on the ceiling or on the wall with the top of the detector between 6 to 12 inches from the ceiling; and/or
• in each story within a building, including basements and cellars, but not crawlspaces or uninhabited attics.

Smoke alarms should not be installed in the following locations:

• near heating or air-conditioning supply and return vents;
• near a kitchen appliance;
• near windows, ceiling fans or bathrooms equipped with a shower or tub;
• where ambient conditions, including humidity and temperature, are outside the limits specified by the manufacturer's instructions;
• within unfinished attics or garages, or in other spaces where temperatures can rise or fall beyond the limits set by the manufacturer;
• where the mounting surface could become considerably warmer or cooler than the rest of the room, such as an inadequately insulated ceiling below an unfinished attic; or
• in dead-air spots, such as the top of a peaked roof or a ceiling-to-wall corner.

Power and Interconnection
Power for the smoke alarms may be hard-wired directly into the building’s electrical system, or it may come from just a battery. Hard-wired smoke detectors are more reliable because the power source cannot be removed or drained, although they will not function in a power outage. Battery-operated units often fail because the battery can be easily removed, dislodged or drained, although these units can be installed almost anywhere. Older buildings might be restricted to battery-powered designs, while newer homes generally offer more options for power sources. If possible, homeowners should install smoke alarms that are hard-wired with a battery backup, especially during a renovation or remodeling project.
Smoke alarms may also be interconnected so that if one becomes triggered, they all sound in unison. Interconnected smoke alarms are typically connected with a wire, but new technology allows them to be interconnected wirelessly. The National Fire Protection Agency requires that smoke alarms be AFCI-protected.
Inspectors can pass the following additional tips on to their clients:

• Parents should stage periodic night-time fire drills to assess whether their children will awaken from the alarm and respond appropriately.
• Never disable a smoke alarm. Use the alarm’s silencing feature to stop nuisance or false alarms triggered by cooking smoke or fireplaces.
• Test smoke alarms monthly, and replace their batteries at least twice per year. Change the batteries when you change your clocks for Daylight Saving Time.  Most models emit a chirping noise when the batteries are low to alert the homeowner that they need replacement.
• Smoke alarms should be replaced when they fail to respond to testing, or every 10 years, whichever is sooner. The radioactive element in ionization smoke alarms will decay beyond usability within 10 years.
• Smoke detectors should be replaced if they become damaged or wet, are accidentally painted over, are exposed to fire or grease, or are triggered without apparent cause.
• Note the sound of the alarm. It should be distinct from other sounds in the house, such as the telephone, doorbell and pool alarm.

 
In summary, smoke alarms are invaluable, life-saving appliances when they are installed properly and adequately maintained. 
 
Brought to you by www.WholeHomeInspectiosLLC.com 
Credit to: Nick Gromicko and InterNACHI

Clothes dryers evaporate the water from wet clothing by blowing hot air past them while they tumble inside a spinning drum. Heat is provided by an electrical heating element or gas burner. Some heavy garment loads can contain more than a gallon of water which, during the drying process, will become airborne water vapor and leave the dryer and home through an exhaust duct (more commonly known as a dryer vent).
 
A vent that exhausts moist air to the home's exterior has a number of requirements:

1. It should be connected. The connection is usually behind the dryer but may be beneath it. Look carefully to make sure it’s actually connected.
2. It should not be restricted. Dryer vents are often made from flexible plastic or metal duct, which may be easily kinked or crushed where they exit the dryer and enter the wall or floor. This is often a problem since dryers tend to be tucked away into small areas with little room to work. Vent elbows are available which is designed to turn 90° in a limited space without restricting the flow of exhaust air. Restrictions should be noted in the inspector's report. Airflow restrictions are a potential fire hazard.
3. One of the reasons that restrictions are a potential fire hazard is that, along with water vapor evaporated out of wet clothes, the exhaust stream carries lint – highly flammable particles of clothing made of cotton and polyester. Lint can accumulate in an exhaust duct, reducing the dryer’s ability to expel heated water vapor, which then accumulates as heat energy within the machine. As the dryer overheats, mechanical failures can trigger sparks, which can cause lint trapped in the dryer vent to burst into flames. This condition can cause the whole house to burst into flames. Fires generally originate within the dryer but spread by escaping through the ventilation duct, incinerating trapped lint, and following its path into the building wall.

InterNACHI believes that house fires caused by dryers are far more common than are generally believed, a fact that can be appreciated upon reviewing statistics from the National Fire Protection Agency. Fires caused by dryers in 2005 were responsible for approximately 13,775 house fires, 418 injuries, 15 deaths, and $196 million in property damage. Most of these incidents occur in residences and are the result of improper lint cleanup and maintenance. Fortunately, these fires are very easy to prevent.

The recommendations outlined below reflect International Residential Code (IRC) SECTION M1502 CLOTHES DRYER EXHAUST guidelines:
M1502.5 Duct construction.
Exhaust ducts shall be constructed of minimum 0.016-inch-thick (0.4 mm) rigid metal ducts, having smooth interior surfaces, with joints running in the direction of air flow. Exhaust ducts shall not be connected with sheet-metal screws or fastening means which extend into the duct.
This means that the flexible, ribbed vents used in the past should no longer be used. They should be noted as a potential fire hazard if observed during an inspection.
M1502.6 Duct length.
The maximum length of a clothes dryer exhaust duct shall not exceed 25 feet (7,620 mm) from the dryer location to the wall or roof termination. The maximum length of the duct shall be reduced 2.5 feet (762 mm) for each 45-degree (0.8 rad) bend, and 5 feet (1,524 mm) for each 90-degree (1.6 rad) bend. The maximum length of the exhaust duct does not include the transition duct.
This means that vents should also be as straight as possible and cannot be longer than 25 feet. Any 90-degree turns in the vent reduce this 25-foot number by 5 feet, since these turns restrict airflow.

A couple of exceptions exist:

1. The IRC will defer to the manufacturer’s instruction, so if the manufacturer’s recommendation permits a longer exhaust vent, that’s acceptable. An inspector probably won’t have the manufacturer’s recommendations, and even if they do, confirming compliance with them exceeds the scope of a General Home Inspection.
2. The IRC will allow large radius bends to be installed to reduce restrictions at turns, but confirming compliance requires performing engineering calculation in accordance with the ASHRAE Fundamentals Handbook, which definitely lies beyond the scope of a General Home Inspection.

M1502.2 Duct termination.
Exhaust ducts shall terminate on the outside of the building or shall be in accordance with the dryer manufacturer’s installation instructions. Exhaust ducts shall terminate not less than 3 feet (914 mm) in any direction from openings into buildings. Exhaust duct terminations shall be equipped with a backdraft damper. Screens shall not be installed at the duct termination.
Inspectors will see many dryer vents terminate in crawlspaces or attics where they deposit moisture, which can encourage the growth of mold, wood decay, or other material problems. Sometimes they will terminate just beneath attic ventilators. This is a defective installation. They must terminate at the exterior and away from a door or window. Also, screens may be present at the duct termination and can accumulate lint and should be noted as improper. 
M1502.3 Duct size.
The diameter of the exhaust duct shall be as required by the clothes dryer’s listing and the manufacturer’s installation instructions.
Look for the exhaust duct size on the data plate.
M1502.4 Transition ducts.
Transition ducts shall not be concealed within construction. Flexible transition ducts used to connect the dryer to the exhaust duct system shall be limited to single lengths not to exceed 8 feet (2438 mm), and shall be listed and labeled in accordance with UL 2158A.
In general, an inspector will not know specific manufacturer’s recommendations or local applicable codes and will not be able to confirm the dryer vent's compliance to them, but will be able to point out issues that may need to be corrected.
 
Brought to you by www.WholeHomeInspectiosLLC.com 
Credit to: Nick Gromicko, Kenton Shepard and InterNACHI 

Check out this article that covers the 5 warning signs that it’s time to clean your dryer vent. This is something that many home owners don’t take the time to do, but is a very important part of ongoing home maintenance.