Coping with vog from Pu'u O'o

(New!Read about Vog from Halemaumau on our web site!)

When a volcano erupts, it produces molten lava in various forms, but the driving force for the eruption comes from the gases that are contained in the lava.  These gases come out of the molten rock at varying pressures and consist of: water vapor, carbon dioxide, sulfur dioxide (SO2), hydrogen, and a variety of other acid and inert gases.  Scientists working near the vent must wear gas masks to protect themselves from the concentrated fumes. Once these gases enter the atmosphere, many react very quickly. Hydrogen reacts with oxygen in the air to form water vapor, and sulfuric acid aerosols (from sulfur dioxide) produce the fume clouds that are carried by the wind and become dispersed into an unpleasant cloud of vog (from the words "volcanic" and "smog").  Over time, the gases continue to react with the atmosphere and ultimately form aerosols of ammonium sulfate that are gradually washed out of the atmosphere by rainfall or a process of settling called dry deposition.

Puu Oo fume Pu'u O'o fuming in 1997.


Currently, Pu’u O’o emits around 2,000 tonnes of SO2 per day, and some of the fumes blow into populated areas. On a trade wind day, northeast winds blow Kilauea’s gases toward the southwest areas of the island and across the ocean, but then thermally-generated winds (caused by Mauna Loa and Mauna Kea heating up during sunlight hours) draw the vog back into a large eddy system offshore of the district of Kona. During daylight hours the vog is brought ashore and upslope on the flanks of Mauna Loa and Hualalai; at night, offshore breezes carry it back out to sea.  When the wind blows from the south, Kona enjoys clean air, and Hilo suffers.  Because Hilo is so much closer to the erupting vents, there is less time for the vog to become dispersed and react with the atmosphere and, as a result, it contains higher concentrations of sulfur dioxide and sulfuric acid aerosols than are found in Kona, and is correspondingly more unpleasant.  In extreme cases, visibility in East Hawaii is less than a couple of miles. When winds are light and variable, the vog accumulates in areas closest to the emitting vents: near Pu‘u O‘o, communities such as Mountain View and Glenwood see high concentrations of vog. 

Puu Oo and D Vent

Photo above, from Mauna Kea: Vog from D Vent (left) and Pu'u O'o (right) blow out to sea on a tradewind day.

Imiloa on a voggy and clear day

Vog is unpleasant to anyone, and can produce headaches as well as irritation to the lungs and eyes at higher concentrations. For people with asthma and other respiratory problems, the effects are much more serious, causing a tightening of the airways in the lungs and making it very difficult to breathe. Studies are being done to learn the long-term effects of vog but, to date, there’s been no clear evidence that vog causes lingering damage to normally healthy individuals.  However, a number of strategies can be used to minimize your exposure to vog’s irritations: when possible, stay indoors with windows and doors closed and sealed. If you have one available to you, use an air conditioner or even a dehumidifier; both will condense water out of the indoor air and, in doing so, will remove the particulate sulfur compounds and acid gases from your indoor air.  You can also reduce your indoor exposure using something as simple as a fan:  in this case, take a hand towel, or, better yet, a piece of cheesecloth, and saturate it with a thin paste of baking soda and water.  Drape the cloth over the face of the fan and turn the fan on at a low or medium speed.  The baking soda will neutralize the sulfur compounds and the moisture will help remove particles from the air.  (You’ll need to keep the cloth damp at all times to ensure that it’s most effective but, as always when operating electrical appliances in the presence of water, be very careful not to get the fan motor wet.)  This should reduce the amount of vog and gases in your indoor air and minimize the irritation from these compounds. 

Ingredients to reduce vog.

Coping with Vog for Hawaii Residents on the Smaller Islands

On the Big Island, the primary irritants in vog are sulfur dioxide (SO2) and tiny sulfuric acid (H2SO4) droplets called aerosols. But as the wind carries the vog far away from Kilauea volcano, the SO2 begins to react with oxygen and moisture in the air to form additional sulfuric acid aerosol particles.   

As more time passes, this acidic vog gradually reacts with small amounts of ammonia that are present in the atmosphere.  (This ammonia is naturally produced by biological decay in moist tropical soils.)  Ammonia, when dissolved in water, is basic, forming NH4OH – the active product in household ammonia – and reacts with the sulfuric acid aerosols to form ammonium sulfate.  By the time the Big Island’s vog plume visits the neighbor islands, the sulfur dioxide and sulfuric acid have already been converted almost entirely to ammonium sulfate [(NH4) 2SO4].  Even though ammonium sulfate particles aren’t acidic, they still can irritate the eyes and throat and can trigger an asthmatic response in sensitive individuals. 

Fortunately for residents of the Small Islands, when the vog comes to visit, it is possible to reduce the concentration of ammonium sulfate in your home. Ammonium sulfate is very soluble in water. All you have to do is drape a wet cheesecloth, or a wet towel, over a box fan in your living room. The fan will draw the air from your living room through the wet cloth, depositing the ammonium sulfate on the towel, where it will immediately dissolve, leaving your air much cleaner. If you have an air conditioner or dehumidifier, these will also help,
although at a higher energy cost, by dissolving the ammonium sulfate
particles in moisture formed on their condenser coils. 

If you must be outdoors, the first rule is “listen to your body”: if you find yourself being fatigued quickly, reduce your level of activity; if you start to have difficulty breathing, then it’s essential that you move to an area that is free of the irritating vog; if your symptoms don’t improve, then get medical assistance ASAP.  Otherwise, stay hydrated when working in a voggy environment – having plenty of water allows your body to clear the particles from your lungs and flush the inhaled sulfur compounds from your body. 

Listen to your body. If vog concentrations become so high that you have difficulty breathing, then, by all means, move out of the area as quickly as you can and seek medical attention if breathing problems persist or your symptoms don’t improve

Vog road views.

When working outdoors, you can greatly reduce your exposure to the sulfur compounds in vog by using a vinyl or rubber gas mask that’s fitted with cartridges rated for acid gases and particulates: many welding supply shops, and even some hardware stores, stock these items.  For optimum performance, make sure that you purchase a mask that is properly fitted to your face and gives a good seal around your nose and mouth.  The best way to do this is to find an experienced professional who works at the store to assist you with the fit and can give you tips on how to get the most benefit from the mask.  It’s also important to purchase the correct cartridges for these masks: you will need cartridges that remove both dust and acid gases; cartridges that will remove these compounds as well as organic vapors are also readily available.  Another important consideration with this type of mask is that their ability to remove gases and aerosols is greatly reduced by the presence of beards and mustaches due to the poor seal between the mask and your skin.  (In critical work environments, where properly fitted masks are required, beards and mustaches are prohibited.)
Gas masks.
Conventional dust masks that are found in most hardware stores are not nearly as effective as the more sophisticated masks intended for acid gas removal.  In times past, when mask technology was less sophisticated, and when gas masks were much less common, the inexpensive dust masks were soaked in a baking soda paste and then allowed to dry before use as a gas mask.  Although some relief was obtained using this strategy, they are a poor second to a properly-fitted gas mask. 

Vog can sometimes be harmful to plants. Native species like uluhe and ohia have adapted to SO2-rich gases, but exotic plants, such as ginger and tibucinia, are susceptible to damage.

Photo above: Leaves of tibucinia and ginger on 27 August 2007, two days after calm winds saturated the Volcano area in dense vog. Photos below show details of leaves.

Tibucinia leaves damaged by vog.

Normal tibucinia leaves.


Ginger leaves damaged by vog. Note undamaged uluhe ferns towards top of this photo.

Normal ginger leaves. The undamaged leaves (in Glenwood) were photographed the same day.