A homeowner can hire a general contractor to oversee a home improvement project that involves multiple trades. A general contractor acts as project manager, providing access to the site, removing debris, coordinating work schedules, and performing some aspects of the work. Sometimes homeowners bypass the general contractor, and hire tradesmen themselves, including plumbers, electricians and roofers. Another strategy is to "do it yourself" (DIY). Several major retailers, such as Home Depot and Lowe's, specialize in selling materials and tools for DIY home improvement. These stores even host classes to educate customers how to do the work themselves.
A smoke detector (or smoke alarm) is a device that detects smoke and issues an alarm to alert nearby people that there is a potential fire. They are an active fire protection device. Because smoke rises, most detectors are mounted on the ceiling or high on a wall. To avoid the nuisance of false alarms, most smoke detectors are mounted away from kitchens. To increase the chances of waking sleeping occupants, most homes have at least one smoke detector near any bedrooms.
Most smoke detectors work either by optical detection or by ionization, but some of them use both detection methods to increase sensitivity. Smoke detectors may operate alone, be interconnected to cause all detectors in an area to sound an alarm if one is triggered, or be integrated into a fire alarm or security system. Smoke detectors with flashing lights are available for the deaf or hearing impaired. A smoke detector cannot detect carbon monoxide to prevent carbon monoxide poisoning unless it has an integrated carbon monoxide detector. They are usually powered by one or more batteries but some can be connected directly to household wiring.
The Xanadu Houses were notable for being built with polyurethane insulation foam rather than concrete, for easy, fast, and cost-effective construction. They were ergonomically designed, and contained some of the earliest home automation systems.