Bug zappers are common mosquito-repelling devices that operate on the principle of insects' phototaxis. They are equipped with ultraviolet (UV) light tubes of specific wavelengths, which are highly attractive to insects like mosquitoes and moths. When insects approach the light tube, they enter the area composed of an electric grid. The grid then releases a high voltage instantaneously, electrocuting the insects.

Most household bug zappers have a voltage ranging from 500 to 1,500 volts. Such high voltage is sufficient to kill tiny insects instantly. However, besides voltage, current is also a crucial factor in determining lethality. The safe current that the human body can withstand is generally below 10 milliamps, while the current output of bug zappers is usually much lower, often 1 milliamp or even less. This means that, theoretically, the current generated by bug zappers is unlikely to directly cause cardiac arrest or other fatal injuries in humans.

Despite the relatively low current of bug zappers, direct contact still poses risks. When the human body touches the electric grid of a bug zapper, the high voltage can cause a strong electric shock, potentially leading to muscle spasms and falls. In special circumstances, such as when reaching for a bug zapper while standing on a high place, a fall could result in severe traumatic injuries and even endanger life. Additionally, for special groups like children, the elderly, or those with heart diseases, even a brief electric shock may trigger health problems.