Mosquito coil is a product burnt for the prevention and elimination of mosquitoes. It is a cylindrical and circular rod. When burnt, its active substances are emitted to repel or kill mosquitoes. There are two types of mosquito coil:
• Mosquito rod
• Mosquito coil
Mosquito coil is different from mosquito spray and lotion because it can prevent and kill the mosquitoes while mosquito spray and lotion are used to prevent the mosquitoes as well as its application aims to smoke the mosquitoes.
Prevention and elimination of mosquitoes
1. It is burnt and turned or placed in the upwind direction or area where prevention and elimination of mosquitoes are needed.
2. When mosquitoes contact with toxic fumes in less concentration that does not make them unable to move or die, they will not come near smoke source or area.
3. When the mosquitoes are poisoned by smoke into their skin, their movement will be reduced and they are finally immobile.
4. After receiving the toxin for a while, the mosquitoes will die.
Ingredient of mosquito coil
The main ingredient in a mosquito coil is pyrethroid that is a synthetic imitator of pyrethrin extracted from flowers, such as chrysanthemum and pyrethrum. This substance is a brownish green powder, decomposes quickly in an alkaline environment, acts in prevention and elimination of insects, and is not harmful to humans and animals. However, the extraction of pyrethrin is very costly, so its imitator was synthesized.
First synthesis of pyrethroid was held around 1950 named allethrin and its initial application was relatively good, but later the mosquitoes resisted it so a new substance has been developed until today.
Main ingredients of mosquito coil
1. Active ingredient is synthetic pyrethroid, such as
• Allethrin is oily and yellow with a boiling point of 140 degrees Celsius, is slightly soluble in water and highly soluble in organic solvents.
• Bioallethrin or d-Allethrin has a greater effect than allethrin and is a sticky liquid with amber color, and is insoluble in water but soluble in organic solvents.
2. Fueling materials, such as wooden powders
3. Binders, such as natural starches
4. Additives, such as colors and preservatives
In addition, some products may contain herbal extracts that provide odor and active effects, such as lemon grass, turmeric, and bergamot.
Mechanism of active effects
Synthetic pyrethroid and natural pyrethrin can have good effects on insects and rarely affect humans and animals because humans and animals have the least rate of absorption into the gastrointestinal tract and skin compared to the insects in which these substances can be well absorbed through chitin on their skin.
When these active ingredients have come into the skin of the insects, they will bind to fat in the insect’s nervous cells and inhibit the function and transmission of nerve impulses making the insects shaking, sclerosis, paralysis and eventually death.
Applications and precautions
1. It is only burnt for generating the smoke.
2. It is burned and placed in the upwind area where mosquitoes need to be repelled.
3. It must always be supported by a supporting material to prevent fire.
4. It must not be eaten.
5. It must not be used in an area where there are children and pregnant or lactating women.
6. In case of allergy to smoke, immediately extinguish and stop using it.
7. It should be used in a place with good ventilation.
8. It should not be used in an area with food or during eating.
9. It should be kept away from children.
10. Hands should always be washed after use.
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Mosquito coil standard in some countries
Mosquito coil is divided into two types by shape as follows:
1.1 Mosquito coil
1.2 Mosquito stick or bar
2.1 Mosquito coil must have a weight of single coil not less than 12.00 grams.
1.2 Mosquito stick or bar must have a weight of single bar not less than 5.50 grams.
3. General requirements
3.1 When both mosquito coil and mosquito stick or bar are separated into a single coil or single bar, they must be broken no more then five percent.
3.2 Strength of mosquito coil
• When tested, mosquito coil must not be broken or cracked as a ring more than eight percent.
• When tested, mosquito stick or bar must not be broken or cracked as a ring more than five percent.
3.3 Active substances
• Active substances in a mosquito coil must include pyrethrin and other synthetic pyrethroids with low toxicity towards guinea pigs or ingredients of such substances.
• A mosquito coil must contain any active substance in an amount specified below:
1. Mosquito coil must contain pyrethrin at 0.37 percent of its dry weight.
2. Mosquito stick or bar must contain pyrethrin at 0.25 percent of its dry weight.
However, for both types, if using other synthetic pyrethroids with low toxicity towards guinea pigs, they must be inversely proportional to the biological efficiency of pyrethrin.
• Synthetic insecticides other than those specified in 3.2 must not be mixed in a mosquito coil.
3.4 Smoke caused by a mosquito coil must have no acute toxicity to humans and warm-blooded animals of all kinds.
3.5 Biological efficiency
A mosquito coil must be able to make the mosquitoes in the species Aedes aegypti and Culex pipiens fatigans knock down not less than 90 percent in 20 minutes and to kill the female mosquitoes in the species Aedes aegypti and Culex pipiens fatigans not less than 50 percent after being left for 24 hours.
3.6 Burning rate
When burning a mosquito coil according to the instructions of use provided by its manufacturer, it must burn continuously within a confined room with a size of 3 meters x 3 meters x 2.5 meters for at least six hours for one mosquito coil and two hours for one mosquito stick.
When collecting samples from their factories, both mosquito coil and mosquito stick must have a humidity of no more than 12 percent.
4.1 Mosquito coil
– Mosquito coil must be packed in a box that can prevent fouling and breaking up. Each box must also include at least one mosquito coil stand.
– Mosquito stick must be packed in boxes to prevent fouling and breaking up.
4.2 Mosquito coil stand
A mosquito coil stand must be made of metal or other non-combustible materials and be able to support a burning mosquito coil.
5. Marking and labeling
5.1 Every mosquito coil box must at least include the number, letter or mark to show the following messages that are visible and clear:
(1) Word “Mosquito coil”
(2) Name and location of factory
(3) Number or letter indicating the manufacturing date (only for carton)
(4) Net weight and number of coils or bars
(5) Common name and percentage of important active ingredients
(6) Warning about use. In the case of a foreign language, its meaning must match the language specified.
6. Analysis of active ingredients and toxicity
6.1 Active ingredients
Active ingredients must be analyzed according to the method prescribed in the latest issue of AOAC in the topic of pesticides.
6.2 Test of acute toxicity
(1) Tool and material
– Glass cabinet with a size of 700 mm x 700 mm x 700 mm
– 10 white rats, each weighing 200 to 300 grams
(2) Test method
A mosquito coil sample is burnt in the glass cabinet for 0.2 grams. Then, the smoke generated is kept within the glass cabinet and ten white rats are left into the glass cabinet. The cabinet is closed and these rats are allowed to inhale the smoke for one hour and then brought out to observe their symptoms.
(3) Test result
If five experimental rats or more die within 48 hours after the test, such mosquito coil sample will be deemed acutely toxic.
6.3 Test of biological efficiency
(1) Tool and material for testing
– Glass cabinet with a size of 700 mm x 700 mm x 700 mm
– 20 female mosquitoes
(2) Test method
A mosquito coil sample is burnt in the glass cabinet for 0.2 grams and the smoke generated is then kept in the cabinet two minutes after the mosquito coil is extinguished. Twenty female mosquitoes that have just eaten the blood and are in perfect conditions are then introduced inside the glass cabinet. Then, the number of mosquitoes falling and tipping over is counted every 5 minutes until 20 minutes and these mosquitoes are sucked into a container that is clean and free of chemical pesticides with a size of 50 mm x 150 mm. The container is closed with gauze and a moistened cotton wool is placed onto the gauze. It is then brought to an area with a temperature of 27 ± 2 ° C and relative humidity 70 to 80 percent over 24 hours and the number of dead mosquitoes is counted.