UV-lamp kills!

14/01 2011

Ultraviolet range as part of the complete UV spectrum produced by the sun is located between waves with length 200 – 400 nm. And it consists:
UV-A – wavelength 315 – 400nm
UV-B – wavelength 280 – 315nm
UV-C – wavelength 200 – 280nm

UV-C waves cause irreversible damage to the living organisms’ cells. That is why they are deadly (lethal damaging). Almost totally these waves are absorbed by the ozone layer of the Earth.

Ultraviolet lamp (UV-lamp) – produced source of ultraviolet radiation, an electric lamp emitting invisible to the human eye UV-waves. Modern lamps for UV printers should not emit harmful ultraviolet wavelength range C, but it is true only for expensive lamps of known brands.

According to the method of obtaining UV lamps can be divided into two types: low pressure lamps and high pressure lamps. Their name indicates how their produced and how they work.

Low pressure lamps are more harmless, but in they are not used in UV printers as source of UV emission due to their low power. Mostly UV printers are equipped with high-pressure lamps.

High-pressure UV-lamp (ND – Nieder Drucken), is a bulb which works with gas pressure in the arc tube and it consists inert gases and mercury vapor under high pressure.

While working high-pressure lamps achieve very high temperature which takes longer time for cooling – about 3-5 minutes after switch off.

Lamp has very high-power UV-radiation in A & B ranges and also in harmful to all living things C range. The main mercury emission wavelength is in the UVC range. Unshielded exposure of the skin or eyes to mercury arc lamps is quite dangerous.

All UV-lamps during working process produce very poisonous gas – ozone. And the lower is emission level of the lamp, it emits more ozone. Most ozone is released when radiation is in C range (lower than 280nm).

Ozone formation is photochemically:

О2>> O + O (hv) Decomposition of molecular oxygen into atoms under the influence of UV radiation
О + О2>> О3 Ozone formation

Ozone is poisonous for humans, animals and plants. Due to the strongly oxidizing properties of ozone, ozone is a primary irritant, affecting especially the eyes and respiratory systems and can be hazardous at even low concentrations. The Canadian Center for Occupation Safety and Health reports that:
"Even very low concentrations of ozone can be harmful to the upper respiratory tract and the lungs. The severity of injury depends on both by the concentration of ozone and the duration of exposure. Severe and permanent lung injury or death could result from even a very short-term exposure to relatively low concentrations."

Ozone leads to premature death, asthma, bronchitis, heart attack, and other cardiopulmonary problems and even cancer.

To protect workers potentially exposed to ozone, OSHA has established a permissible exposure limit (PEL) of 0.1 ppm (29 CFR 1910.1000 table Z-1), calculated as an 8 hour time weighted average. Higher concentrations are especially hazardous and NIOSH has established an Immediately Dangerous to Life and Health Limit (IDLH) of 5 ppm. Work environments where ozone is used or where it is likely to be produced should have adequate ventilation and it is prudent to have a monitor for ozone that will alarm if the concentration exceeds the OSHA PEL.

A study of 450,000 people living in United States cities showed a significant correlation between ozone levels and respiratory illness over the 18-year follow-up period. The study revealed that people living in cities with high ozone levels such as Houston or Los Angeles had an over 30% increased risk of dying from lung disease. 

In the EU, the current target value for ozone concentrations is 120 µg/m³ which is about 60ppb. This target applies to all member states in accordance with Directive 2008/50/EC. Ozone concentration is measured as a maximum daily mean of 8 hour averages and the target should not be exceeded on more than 25 calendar days per year, starting from January 2010. Whilst the directive requires in the future a strict compliance with 120 µg/m³ limit (i.e. mean ozone concentration not to be exceeded on any day of the year), there is no date set for this requirement and this is treated as a long-term objective. 

Also all UV-lamps contain mercury and heavy-metals compounds; because it is based on their work principle. And all heavy-metals compounds are very toxic poisons and carcinogenic.

More about mercury poisoning

Best examples of UV-lamps from most famous brands consist about 15mg of mercury. Other lamps’ mercury consistency can be up to 100mg. Experts counted that every year only in UV-printers industry more than 13 kg of mercury is released to the environment. But it is also released in the form of compounds, which are more toxic and poisonous then metal mercury and quantity of these compounds is much more than weight of released metal mercury.

All this drawbacks are absent in UV-LEDs: