| CADR | Look for these numbers when comparing portable room air cleaners. |
| Canadian Standards Association (CSA) | An organization that maintains standards used to certify products for safety, rate products for performance and to complement the requirements in codes. |
| Candles | They create a warm, cozy atmosphere — and present some hazards as well. |
| Capital Cost | The installed cost of equipment. |
| Carbon Dioxide (CO2) | A colorless, odorless gas released in exhaled breath, or by combustion processes. |
| Carbon Monoxide (CO) | A colorless, odorless, poisonous gas released during the incomplete combustion of carbon-containing fuels. |
| Carbon Monoxide Alarm | Every home should have at least one CO detector. |
| Carbon-Dioxide Sensor | A device that senses the carbon dioxide concentration in the air and can be used to control a ventilation system. |
| Carcinogen | A substance that tends to cause cancer. |
| Castile Soap | Soap made from a variety of vegetable oils that is a healthy alternative for allergy sufferers and those with sensitive skin. |
| Category A Room | A room, such as a bedroom or living room, that is often occupied for long periods and requires general ventilation. |
| Category B Room | A room, such as a kitchen or bathroom, in which moisture or pollutants are generated, that has special ventilation requirements. |
| Caulk | A product that’s essential to a well sealed home. |
| Central Vacuum System | Central vacuums have a number of advantages over portable units. |
| Central Ventilation | Any general-ventilation strategy, i.e., balanced, central-supply or central-exhaust; with or without heat or energy recovery. |
| Central-Exhaust Ventilation | A general-ventilation strategy that uses an exhaust fan to remove air from a house. |
| Central-Supply Ventilation | A general ventilation strategy that uses either a supply ventilation fan or a forced-air heating/cooling fan to draw air into a house. |
| Centrifugal Fan | A ventilating fan with blades resembling a squirrel cage or a hamster wheel, often used in furnaces and ventilating devices. |
| CFL | Compact fluorescent lamps offer great energy savings over traditional incandescent or halogen lighting. There are trade-offs, however. |
| Chemical Sensitivity | Chemical sensitivity is hypersensitivity or intolerance to numerous chemicals at very low exposures or concentrations. |
| Chimney | A vertical structure or conduit that usually carries combustion by-products out of a house. |
| Chlorofluorocarbons (CFCs) | Chlorofluorocarbons define a category of chemicals which contain chlorine, fluorine and carbon. |
| Circulating Air | Air that moves from room to room or throughout a house. |
| Combustion Air | Air that enters a house specifically to be used in the combustion of a fuel. |
| Combustion By-Products | Gases and particulates released during the burning of a fuel. |
| Combustion Gases | Gases released during the combustion of heating and other fuels that can include carbon monoxide, sulfur dioxide, and nitrogen dioxide. |
| Combustion-Air Duct | A duct through which combustion air travels from the outdoors to a combustion device. |
| Concrete | Durable, versatile material made of four main ingredients: cement, aggregate, water, and admixtures. |
| Concrete-Slab Foundations | Easily constructed in a healthy manner, it can be part of a house foundation or built separately from the footings and foundation wall. |
| Condensation | The changing of a gas or vapor into a liquid, accompanied by the release of heat. |
| Conditioned Space | The part of a house, within the building envelope, that is kept at comfortable controlled temperature and humidity levels. |
| Controlled Pressure | An air-pressure difference between the indoors and the outdoors, purposefully induced by ventilation equipment. |
| Controlled Ventilation | Purposeful air movement into and out of a building in a regular way. |
| Convective Air Currents | The movement of air resulting from heat transference through the air by convection. |
| Crawl Space Foundations | Unlike basement foundations, a crawl space is not considered part of a home’s living space. Crawl spaces are usually accessed only to repair pipes, ducts or mechanical equipment. |
| Cubic Feet Per Minute (CFM) | A unit of measurement used to rate a fan’s capacity. |
