Air fresheners are consumer products used in homes or commercial products used in restrooms that typically emit fragrance. There are many different methods and brands of air freshener. Some of the different types of air fresheners include sprays, candles, oils, gels, beads, and plug-ins. There are also solid and passive versions, which use ceramic material and water based ingredients - these combine and create a 'multi-phasing' effect which provides a constantly evolving fragrance. Some air fresheners have been known to have chemicals that provoke allergy and asthma symptoms raising argument about how safe it is to use. However, some air fresheners are VOC exempt, such as a passive, multi-phasing air freshener, that reduces the effects. Air freshening is not only limited to modern day sprays, air freshening also can involve the use of organic and everyday house hold items. Although air freshener is primarily used for odor elimination some people simply use air freshener for the pleasant odors they emit.