How long does ozone stay in the atmosphere

According to the U. That third oxygen atom is considered unstable, meaning it can detach and re-attach to molecules of other substances, thereby altering their chemical structure entirely. As the name suggests, ozone generators produce the gas ozone.

Ozone, as we previously mentioned, is known for its excellent sanitation capabilities. Because of this, many people opt to use these devices in their homes to remove organic compounds including pollutants, bacteria, and lingering odor from the air.

Some brands, such as the OGBlu by Home Sanitizer Solutions, feature additional features like built-in UV lamps to further reduce the risk of bacteria and viruses. According to the Home Air Advisor , ozone lasts between 30 minutes and 4 hours before it converts back into oxygen. Higher levels of ozone concentration generally take 3 to 4 hours to dissipate, while lower levels can clear out in about 2 hours. For extra safety precautions, it is suggested to wait at least 4 hours before returning to the room.

When used properly, ozone generators are safe and sanitizing. In the troposphere, temperature decreases with increasing altitude, allowing convection—the rapid vertical mixing of air parcels—to occur. At its border with the stratosphere, temperature begins to rise and convection essentially stops.

In the absence of convection, a slow exchange of air occurs across the tropospheric-stratospheric border. CFCs are transported to the stratosphere by this process, which also allows ozone exchange between the atmospheric levels. The net transfer of ozone is from the stratosphere to the troposphere, because of the higher levels of ozone in the upper level.

This exchange, however, plays only a minor role in determining ozone abundances in both the stratosphere and troposphere. The Montreal Protocol has banned production of CFCs throughout the world, and the stratospheric ozone layer is expected to fully recover over the next 50 to years.

Major efforts are being undertaken to implement emission control strategies that will limit tropospheric ozone to less than prescribed levels. These initiatives are challenged by global industrialization and the fact that tropospheric ozone is affected by pollutants emitted both locally and from distant upwind sources, sometimes from other countries or continents. Sign up for our email newsletter. Already a subscriber? Sign in. Thanks for reading Scientific American. Though ozone in the stratosphere is protective, ozone in the atmosphere - which is the air we breathe - can be harmful to the respiratory system.

Harmful levels of ozone can be produced by the interaction of sunlight with certain chemicals emitted to the environment e. These harmful concentrations of ozone in the atmosphere are often accompanied by high concentrations of other pollutants, including nitrogen dioxide, fine particles and hydrocarbons.

Whether pure or mixed with other chemicals, ozone can be harmful to health. Available scientific evidence shows that at concentrations that do not exceed public health standards, ozone has little potential to remove indoor air contaminants.

Some manufacturers or vendors suggest that ozone will render almost every chemical contaminant harmless by producing a chemical reaction whose only by-products are carbon dioxide, oxygen and water. This is misleading. There is evidence to show that at concentrations that do not exceed public health standards, ozone is not effective at removing many odor-causing chemicals. If used at concentrations that do not exceed public health standards, ozone applied to indoor air does not effectively remove viruses, bacteria, mold, or other biological pollutants.

There are many brands and models of ozone generators on the market. They vary in the amount of ozone they can produce. In many circumstances, the use of an ozone generator may not result in ozone concentrations that exceed public health standards. But many factors affect the indoor concentration of ozone so that under some conditions ozone concentrations may exceed public health standards. The actual concentration of ozone produced by an ozone generator depends on many factors.

Concentrations will be higher if a more powerful device or more than one device is used, if a device is placed in a small space rather than a large space, if interior doors are closed rather than open and, if the room has fewer rather than more materials and furnishings that adsorb or react with ozone and, provided that outdoor concentrations of ozone are low, if there is less rather than more outdoor air ventilation.

The concentration is highest at the point where the ozone exits from the device, and generally decreases as one moves further away. Manufacturers and vendors advise users to size the device properly to the space or spaces in which it is used. Further, some literature distributed by vendors suggests that users err on the side of operating a more powerful machine than would normally be appropriate for the intended space, the rationale being that the user may move in the future, or may want to use the machine in a larger space later on.

Using a more powerful machine increases the risk of excessive ozone exposure. Ozone generators typically provide a control setting by which the ozone output can be adjusted. The ozone output of these devices is usually not proportional to the control setting.

That is, a setting at medium does not necessarily generate an ozone level that is halfway between the levels at low and high. The relationship between the control setting and the output varies considerably among devices, although most appear to elevate the ozone output much more than one would expect as the control setting is increased from low to high. In experiments to date, the high setting in some devices generated 10 times the level obtained at the medium setting US EPA, However, room size is only one factor affecting ozone levels in the room.

In addition to adjusting the control setting to the size of the room, users have sometimes been advised to lower the ozone setting if they can smell the ozone. While the smell of ozone may indicate that the concentration is too high, lack of odor does not guarantee that levels are safe.

At least one manufacturer is offering units with an ozone sensor that turns the ozone generator on and off with the intent of maintaining ozone concentrations in the space below health standards. EPA will report its findings as the results of this research become available.

Ozone has been extensively used for water purification, but ozone chemistry in water is not the same as ozone chemistry in air. High concentrations of ozone in air, when people are not present , are sometimes used to help decontaminate an unoccupied space from certain chemical or biological contaminants or odors e. However, little is known about the chemical by-products left behind by these processes Dunston and Spivak, While high concentrations of ozone in air may sometimes be appropriate in these circumstances, conditions should be sufficiently controlled to insure that no person or pet becomes exposed.

Ozone can adversely affect indoor plants, and damage materials such as rubber, electrical wire coatings and fabrics and art work containing susceptible dyes and pigments U. EPA, a. The three most common approaches to reducing indoor air pollution , in order of effectiveness, are:.