Liquid repellents are now widely used to repel mosquitoes. The Liquidator mosquito repellent has a graphite rod in the middle and the bottle is filled with the repellent. There is a heater coil in the liquidator. The repellent chemical when comes in to contact with the heated rod turns into fume which disables the sensors of the mosquitoes. The fumes produced by the repellent blocks the chemo sensors of mosquitoes so that they cannot identify human beings.
Liquid mosquito repellents contain chemicals such as ,Prallelthrin , Allethrin etc. Of these the most commonly used one is Pralletrhin. Prallethrin is a pyrethroid chemical used as an insecticide. It is an Yellow to amber viscous liquid. d -trans-Prallethrin is a potent contact insecticide which produces a rapid knock-down, with same chemical and physical properties as Prallethrin.d-trans-Allethrin is also a powerful repellent used in mosquito coil and liquid.
These chemicals in the form of vapors block the chemo reception and also the respiratory tracts of the mosquitoes and thus they avoid the hostile situation.The chemical repellents used as mosquito repellents are toxic substances. Even though the concentration of the ingredient is in a safe level, this may cause allergic and respiratory problems in some persons. Precautions are recommended by the manufacturers and these include
1. Avoid inhalation and skin contact.
2. Wash contaminated skin & eyes.
3. Destroy empty containers after use.
4. Keep away from food stuff and animal feeds.
Most common natural repellents used are oils extracted from plants. These natural products will effectively repel mosquitoes, but they require more frequent reapplication (at least every 2 hours). Citronella Oil, Lemon, Eucalyptus Oil, Cinnamon Oil, Castor Oil, Rosemary Oil, Lemongrass Oil, Cedar Oil, Peppermint Oil, Clove Oil, Garlic Oil etc are found to be effective against mosquitoes.
It is a plant-derived substance, used as an insecticide. Pyrethrum comes from the flowers of the daisy Chrysanthemum cinerariifolium. Pyrethrum and its modified forms are used to prepare mosquito coils.mats liquids etc. Natural pyrethrins are highly fat soluble, but are easily degraded and thus do not accumulate in the body.
The Pyrethrins are a pair of natural organic compounds that have potent insecticidal activity Pyrethrin I and pyrethrin II are structurally related esters with a cyclopropane core. They are viscous liquids that oxidize to become inactivated. They are non-persistent, being biodegradable, and break down on exposure to light or oxygen.
Synthetic Pyrethroids, is the synthetic form of Pyrethrum found in the chrysanthemum flower. The compounds have low toxicity for humans and birds, and are used in many household insecticides such as RAID as well as mosquito coils. They act by paralyzing the insect before it kills. They are also used as an ultra low volume (ULV) spray for outdoor mosquito control.
The Allethrins are a pair of related synthetic compounds used in insecticides. They are synthetic pyrethroids is used mainly for the control of flies and mosquitoes in the home, flying and crawling insects on farm animals, and fleas and ticks on dogs and cats. It is formulated as aerosols (1 – 6 g/litre), sprays, dusts (1%), smoke coils, and mats. It is used alone or combined with synergists (e.g.piperonyl butoxide and N- octylbicycloheptene dicarboximide) or other insecticides (e.g., fenitrothion). It is also available in the form of emulsifiable concentrates and wettable powders.
Bioallethrin is more than twice as effective as allethrin and is mainly used to control household insects. It is formulated as aerosols and sprays with synergists and/or other insecticides (e.g., d-phenothrin or deltamethrin).
DEET is the most common active ingredient proven to prevent mosquito bites. It is a member of the toluene chemical family and DEET is slightly yellow liquid at room temperature and can be prepared by converting m-toluic acid to acyl chloride and reacting with diehtylamine.
Mosquito mats are available as chips. The chemicals are coated as thin layers on both sides of the chip. The chips are heated in an electronic heater and the vapor repels mosquitoes.
Source: Mohan's electronics blog