Mosquito coil

A mosquito coil is a mosquito repelling
incense , usually shaped into a spiral, and
typically made from a dried paste of
pyrethrum powder. The coil is usually held
at the center of the spiral, suspending it in
the air, or wedged by two pieces of
fireproof nettings to allow continuous
smoldering. Burning usually begins at the
outer end of the spiral and progresses
slowly toward the centre of the spiral,
producing a mosquito-repellent smoke. [1] A
typical mosquito coil can measure around
15 cm in diameter and lasts around 8
hours. Mosquito coils are widely used in
Asia, Africa, South America and Australia.
[2]


Invention

Pyrethrum was used for centuries as an
insecticide in Persia and Europe,[3] and the
mosquito coil was developed around the
1890s by a Japanese business man,
Eiichiro Ueyama. At that time in Japan,
people usually mixed pyrethrum powder
with sawdust and burned it in a brazier or
incense burner to repel mosquitoes.
Initially, Ueyama created incense sticks
mixed from starch powder, dried mandarin
orange skin powder, and pyrethrum powder.
However, the bar-shaped mosquito sticks
quickly burned up in about 40 minutes, too
brief for a long repelling action. In 1895,
his wife Yuki proposed making the sticks
thicker and longer, and curling them in
spirals. In 1902, after a series of trials and
errors, he finally obtained the desired
incense burning effect out of a spiral-
shaped mosquito repellent. The method
involved cutting from a thick bar of incense
to a certain length and manually winding
it. This method continued to be used until
1957, where mass production was made
possible through machine punching,
making a far larger manufacturing scale
possible. [4][5] After the Second World War,
his company, Dainihon Jochugiku Co. Ltd ,
set up joint-venture firms in various
countries, such as China and Thailand, to
produce products suited to local
conditions. [5]



Ingredients

Active ingredients found in mosquito coils
may include: [6]

1, Pyrethrum - a natural, powdered material
from a kind of chrysanthemum plant;
performance moderate

2, Pyrethrins - an extract of the insecticidal
chemicals in pyrethrum

3, Allethrin - sometimes d-trans-allethrin,
the first synthetic pyrethroid

4, Esbiothrin - a form of allethrin

5, Butylated hydroxytoluene (BHT) - an
optional additive to prevent pyrethroid from
oxidizing during burning

6, Piperonyl butoxide (PBO) - an optional
additive to improve the effectiveness of
pyrethroid

7, N-Octyl bicycloheptene dicarboximide
(MGK 264) - an optional additive to
improve the effectiveness of a pyrethroid


Advantages

Modern day Mosquito coils burn without
flame for around twelve hours. In
quantitative tests, they provide about 80%
protection. [6] Mosquito coils are also
inexpensive and easy to use. They are
portable and fit into normal household
practices of lighting candles or incense.


Disadvantages

Mosquito coils can be hazardous. In 1999,
sparks from mosquito coils ignited a fire
that swept through a three-story dormitory
building at a summer camp in South Korea;
23 people, including 19 children, died in the
blaze. [7] Recent studies showed that the
smoke generated from a burning mosquito
coil is of certain health concerns – oney
burning mosquito coil produces the same
amount of particulate mass (diameter up to
2.5 μm) as 75-137 burning cigarettes
would; and the emission of formaldehyde
from one burning coil can be as high as
that released from 51 burning cigarettes. [2]


http://en.m.wikipedia.org/wiki/Mosquito_coil