Volcanic pollution is threefold, involving sulfur dioxide (SO2) pollution, sulfate (SO4) pollution, and combustion pollution from vegetation. SO2 gas is emitted from the eruption, but in the atmosphere it transforms into SO4 which clumps together into particles that appear as PM2.5 and PM1 on particulate matter monitors. This transformation can take anywhere from a few hours to several days (depending on the weather), so it often happens that SO2 is measured but no sulfate—or vice versa.
Volcanic smog appears when SO2 gas is transformed into SO4 particles, which create a bluish mist. Because these are fine particles, they are measured as particulate matter, or PM2.5 and PM1. PM stands for "particulate matter," and the number refers to the particle size in micrometers (µm). So a PM2.5 reading means all particles smaller than 2.5 µm in diameter. The most common PM measurements are PM10, PM2.5, and PM1. Since PM10 measures all particles under 10 µm, PM2.5 and PM1 are included in the PM10 value, and PM1 is included in the PM2.5 value. If the ratio of PM2.5 and PM1 is high relative to PM10 (e.g., PM2.5 is about half of PM10), this suggests the presence of volcanic smog.
Not all monitors measure the same thing, so they may display different color indicators. To stay on the safe side, it's best to go by the “worst” reading from the nearest monitor. For example, if an SO2 monitor shows green but a nearby PM2.5 monitor shows red, this suggests that most of the SO2 has converted into SO4 and is therefore no longer detected. However, both substances are irritating, so if either is elevated, we advise people to stay indoors, close windows, turn off ventilation systems, and limit physical exertion. This is especially important for sensitive groups such as children, the elderly, and those with pre-existing respiratory conditions. Children should also not sleep outdoors in strollers.
Monitors have the limitation that they measure locally in a small area. SO2 pollution can travel in narrow plumes, meaning it might be high in one spot and low just a few kilometers away. Additionally, irritation may appear sometime after exposure has ended, as cumulative effects. It’s helpful to check historical readings, which can be done by clicking the “>” tab in the top left corner on airquality.is, selecting a monitoring station and time period to view data in table or graph form. Ultimately, if people experience eye or respiratory irritation during an active volcanic eruption, it is likely due to volcanic pollution. In that case, we advise staying indoors, closing windows, turning off ventilation systems, and limiting exertion. This is especially important for sensitive groups such as children, the elderly, and those with pre-existing respiratory conditions. Children should also not sleep outdoors in strollers.
High-quality air quality monitors are usually very sophisticated and accurate, making them expensive to purchase, maintain, and operate. The ongoing volcanic activity on the Reykjanes Peninsula is unprecedented since air quality monitoring began in Iceland, and since it started significant effort has been made to improve monitoring, data presentation, and public information. On the Reykjanes Peninsula and in the capital area, one of the densest SO2 monitoring networks in Europe has been established, and work is ongoing to install more monitors. There are cheaper monitors available from various manufacturers, but experience shows they are much less accurate and often show vastly inflated readings.
There are no specialized automatic volcanic haze monitors. Instead, particulate matter monitoring is used, which provides a very good approximation of volcanic smog concentration.
The placement of monitors is primarily determined by the likelihood that air quality could exceed health protection thresholds or when it's deemed especially important to monitor a certain location. Therefore, some monitors are located near heavy traffic roads in the capital region or near industrial areas, as part of environmental monitoring, or by schools, as children are generally more sensitive to air pollution. In smaller municipalities with less traffic and industry, it is much less likely for air pollution to exceed health protection limits. Many new monitors have recently been installed on the Reykjanes Peninsula to respond to increased volcanic activity in the area.