A germicidal purifier is a device used to cleanse air or water to make it suitable for human consumption. These purifiers are available for both home and industrial use. Though there are many different ways to create a germicidal purifier to filter air and water, the term "germicidal" is most often used in conjunction with ultraviolet disinfection.
Whether they are built for water or air, many germicidal purifiers make use of ultraviolet, or UV, light. The water or air is exposed to a bulb, which gives out UV radiation. Prolonged exposure alters the deoxyribonucleic acid, or DNA, of many germs, rendering them unable to replicate themselves.
A low-tech method of creating a germicidal purifier involves exposing water to UV light. This technique is called solar cleansing. The untreated water is poured into clear plastic bottles, which are placed on a roof in full sunlight. After a minimum of six hours of full exposure, many of the germs will be killed. This method is recommended for survivalists or residents of poor countries where commercial germicidal purifiers aren't always available.
Other methods of cleansing used in a germicidal purifier include filtering, adding disinfectants to the water, and exposing it to ozone. Filters can be made of sand, lava, or charcoal. They can screen out large impurities in water or air and often require the element to be pumped through them. Fluoride and chlorine are disinfectants often added to city water supplies to kill germs and prevent tooth decay. Ozone purifiers work by oxygenating the water more than is tolerable for most microorganisms.
Home air and water purification devices are sold to people with allergies or who are concerned about impurities in their water or air causing illness. They come in a range of designs and prices and have filters, which must be separately bought and replaced regularly. Home air purifiers will sometimes add chemicals to the air, while most home water purification devices work by UV radiation or filtration, which leaves no additives behind.
A germicidal purifier may be used on a large-scale by a cleanup company or at the site of a natural disaster. Water-processing plants also make use of the many kinds of germicidal purifiers. A germicidal purifier using ozone is too intense for day-to-day use and is usually only used for cleanup after fires or by forensics teams. It is, however, sometimes used in home purifiers.