Dr. Carol Blocksome and others at Kansas State University have developed a video that explains prescribed burning in the Flint Hills region of Kansas to an urban audience. Numerous people from all aspects of fire were interviewed in making the video. Their participation has been critical to the success of the video. Dr. Blocksome stated they had many excellent interviews and were not able to use much more than a small fraction of the footage in the 26 minute video, which was the time allotted to them by the television station.
A fire prescription is a set of conditions under which a fire will be set to meet land management objectives. It is based on scientific research and experience.
First, determine the management goals and objectives of the area to be burned. Next, develop a fire prescription for that area. Prescriptions may require specialized personnel, tactics, training, equipment, and firebreaks. Consultation with a fire management specialist will help in developing custom fire prescriptions that will meet the objectives of the unit.
Rule 1. For those in the process of learning to burn or with limited experience, use the 60:40 Rule. The 60:40 rule states that you burn with an air temperature of less than 60°F, a relative humidity greater than 40%, and a wind speed of 5-15 mph measured at 6 feet above the surface of the ground.
Rule 2. For those concerned about weather conditions changing out of the prescription, use the Rule of Halves. This rule is used in the field to predict changes in fire behavior. When the air temperature increases by 20°F, the relative humidity decreases by 50%. For example, if the air temperature changes from 60°F with 40% relative humidity to 80°F, the relative humidity will change from 40% to 20%. A fire that can be conducted safely at 40% relative humidity may pose a safety risk at 20%.
Rule 3. In most cases, do not burn if there is a forecasted frontal passage or wind shift within 12 hours.
Rule 4. In general, the width of firebreak on the down wind side of the area to be burned should be 10 times the height of flammable vegetation. Firebreaks are usually a combination of bare ground, mowed strips, and backfired strips. In woodlands, leaf blowers are often used to create a bareground fire break. Landscape features such as streams and roads also can make adequete firebreaks. If the firebreak is insufficient, you may experience a fire escape.
Rule 5. If the conditions are not right, including all parts of the prescription (adequate personnel, equipment, weather conditions, etc.), do not start the fire. Wait until everything is right.
Rule 6. If the fire is not going well, put it out.
Rule 7. Do not leave the fire until it is completely out, that is no visable smoke for at least one hour.
Trees and brush should never be cut, dozed and piled prior to a prescribed burn. This will complicate the burn and increase spotfire chances. Research has shown that brush piles can cause spotfires up to 500 feet down wind. If piling is necessary, push piles 300 feet into the burn unit, keep piles small and keep an eye down wind of them during the prescribed burn.
Burning brush piles in the summer when surrounding plants are green.
The best time to burn brush piles is after the prescribed fire has been conducted. Burn when the area is black or let the burn unit green up. Safe times to burn brush piles include early summer months when surrounding grass is green and and well hydrated (May and June for much of the Great Plains). Burning in the winter with dormant fuels and dry conditions can cause problems, even when burning brush piles with snow on the ground. Large brushpiles can burn for days, sometimes weeks, and when the snow melts the spotfire risk increases.
Burns with high temperatures and low humidity are for experienced fire bosses and crews. Look back at the general guidelines for prescribed fires.
Research has shown that if a prescribed fire is conducted with relative humidity under 25% there is a 100% probability of a spotfire occurring. There is only a 46% chance of a spotfire when the humidity is between 25% and 29%. Spotfires significantly decrease when prescribed fires are conducted when the relative humidity is higher than 40%. This does not suggest that prescribed fires cannot be conducted under 40% humidity, but is one of the many decisions that needs to be made when planning a prescribed burn.
Burning under good smoke dispersion conditions.
Burning on days that have good smoke dispersion can reduce smoke effects. Before beginning a prescribed fire, the effects of smoke downwind must be considered. Burning so that smoke disperses away from sensitive areas (residential areas, hospitals, highways, and airports) must be considered in the burn plan. If smoke is a concern, consider burning dry fuels over moist fuels. Backfires also tend to produce less smoke than flank or headfires.
For more detailed information about prescribed fire prescriptions, view this fact sheet: http://pods.dasnr.okstate.edu/docushare/dsweb/Get/Document-2704/NREM-2878web.pdf
What are the components of smoke from wildland burning?
All wildland fires produce smoke plumes that contain embers, particulates, nitrous oxides, and volatile organic compounds. In grassland prescribed fires, embers generally drop out rapidly, frequently within the burned area. Particulates and gasses, however, can cause air quality problems downwind if not managed.
Particulates are tiny bits of solids or liquids, and are designated as PM10 or PM2.5, which refers to the diameter of the particle as measured by its ability to pass through 10 microns or 2.5 microns filters, respectively. Because of their larger size, PM10 particles tend to drop out of the air more rapidly than PM2.5 particles.
Both types of particulate matter can cause breathing problems, especially for those with respiratory or circulatory diseases. PM2.5 is especially dangerous, as its small size allows it to be drawn deeply into the lungs. Both types of particulate matter are cleaned from the air by rain.
Nitrous oxides (NOx) and volatile organic compounds (VOC) are gasses released during combustion. Although they are not ozone, they combine in the presence of sunshine to form ozone. Ozone is not cleaned from the air by rainfall. It can disappear during the night, only to reform the following day. Ozone plumes hang together and are not dissipated by rain. Because of these characteristics, these plumes can travel hundreds of miles from the source.
What are the effects of smoke?
Ozone can also cause health problems for those with respiratory and cardiac diseases. Ozone and particulate matter can combine and cause an air quality problem called regional haze. This is an aesthetic as well as a health problem. Regional haze is most likely to form during low wind conditions and weather inversions.
Smoke combined with fog can create a visually impenetrable condition that is sometimes known as superfog. It tends to settle in low-lying areas such as valleys and stream corridors. Superfog is often associated with multiple fatal collisions, as motorists encounter the fog without warning and road conditions change from excellent visibility to near total darkness in a matter of seconds.
How can I reduce smoke from controlled burns?
When conducting prescribed burns, it’s important to be aware of problems that may result from the smoke you produce if you are near people who will be impacted by your smoke. If there are many prescribed fires burning at the same time in your area, the combined smoke plume from these fires can travel hundreds of miles and cause air quality problems in downwind areas. Burning on days when smoke dispersal is high will improve air quality both locally and downwind. Burning when fuels are dry will also increase combustion and reduce smoke production.
Read more at: http://www.ksre.ksu.edu/bookstore/pubs/MF3072.pdf
Reducing the impacts of smoke should be considered when planning a prescribed fire. Smoke management is not really about the reduction of emissions, but the redistribution of emissions, which is done by choosing wind direction, atmospheric conditions (such as mixing height), and ignition techniques to manage the convection. Perhaps less discussed are ignition techniques themselves. Following are some basic guidelines when planning ignition techniques to reduce smoke emissions. We must be aware, however, of potential tradeoffs between reduced smoke emissions and achieving ecological goals with fire.
How to influence smoke
Smoke includes a mix of chemicals including bits of the unconsumed fuel. Unconsumed fuel on the ground leads to smoldering phase burning. Smoldering produces more smoke than burning in the flaming stage of ignition. Ignition techniques that lead to more complete combustion should produce less smoke than other techniques. Here are some examples.
1. Backing fire. Backing fires (fires that burn against the wind) consume fuels more completely than head or flanking fires; thus, backing fires generally produce less smoke. Tradeoffs include increased time to complete burns because backing fires move more slowly, and flame lengths are relatively short so may not provide sufficient heat to kill some plants.
2. Headfire. Headfires (burn with the wind) move more quickly, produce more heat, generally consume fuel less completely, and produce taller flame lengths. Incomplete fuel combustion results in greater smoke production than backfires. Although headfires may produce more smoke, they may be used to complete a fire more quickly, thereby reducing the overall burn time. Furthermore, the speed and intensity of headfires releases more heat that can help the smoke to rise in a column, facilitating dispersal at higher levels in the atmosphere. Headfires can also be more challenging to conduct safely if used exclusively.
3. Ring headfire. This technique uses a combination of back, flank, and head fires. Backfires and flanking fires are used around the perimeter to create a safe black zone to send the headfire towards. This technique is often used because of its safety and compromise in completion time. The backfire portion of the fireline may be less smoky, but generates steady amounts of heat so when the headfire begins, smoke forms a column and is dispersed aloft. The placement of the head and backfire zones can be adjusted to avoid smoke in sensitive areas and apply the right flame length/residence time combination to treat fuels in different parts of the burn unit. Ring headfires are generally not recommended when wildlife is a consideration because animals may be entrapped.
4. Additional techniques, such as chevron, single point ignition, and strip head-firing, are often used to speed the development of a safe zone around a burn unit perimeter. These techniques can also be applied to create pulses of heat to lift smoke aloft. Keep in mind that head fires typically produce more smoke through incomplete ignition and subsequent smoldering, but generate high levels of heat. Size of the strips used with these techniques can make a huge difference. Large strips may produce more smoke, but because of increased heat production, the smoke is lofted higher more quickly than with smaller strips. A quick completion of a burn can reduce the time of potential exposure to smoke though generating more smoke in the short period.
When choosing an ignition technique, consider many factors, including smoke, and prioritize them with respect to objectives and risks.
Resources: NWCG Fire Use Working Team. 2001. Smoke management guide for prescribed and wildland fire. NFES 1279, PMS 420-2 or an older version from Feb. 1985.
NWCG. 2012. Glossary of wildland fire terminology. PMS 205. http://www.nwcg.gov/pms/pubs/glossary/pms205.pdf
Native Americans placed great value on the four elements of life, earth, water, air and fire. They recognized, as we do today, that fire is the most powerful land management tool. The 4.8 million acre Flint Hills region of Kansas is the largest remaining expanse of tallgrass prairie in North America. Prescribed fire is routinely practiced in the region to enhance livestock forage quality, control invasive species, provide grassland wildlife habitat and improve plant vigor. But where there is fire, there is smoke, and there are public health concerns when excessive smoke is in the atmosphere. Ground level ozone can have serious public health consequences and major cities adjacent to the Flint Hills, have recorded excessive ozone levels resulting from Flint Hills prescribed fire. A collaborative effort including the Kansas Dept of Health & Environment, EPA, K-State Research & Extension, Kansas Livestock Association and other groups completed the Flint Hills smoke management plan in December, 2010, with the objective of reducing health concerns from prescribed fire, while retaining it as a land management tool. The plan established a website of “best smoke management practices” and a comprehensive education and outreach effort for land managers was implemented, involving prescribed fire schools, news articles and radio airplay. Results of the plan are positive, indicating that Kansas has responded to the smoke issue appropriately and will retain prescribed fire as a management practice that maintains both the tallgrass prairie of the hills, and the air quality of adjacent metro areas. The inter-relationships of earth, water, air and fire are continual, each impacting the other. The Kansas Flint Hills now has a plan to ensure harmony of these essential elements of life.
A prescribed fire in the Kansas Flint Hills
Prescribed Fire in Tallgrass Prairie
The Flint Hills Smoke Management Plan is a collaborative effort designed to maintain the benefit of prescribed fire on the private grasslands of the Flint Hills, while also protecting the air quality of ajor metropolitan areas such as Kansas City and Wichita. The Flint Hills have particular environmental implications, as they are the largest expanse of tallgrass prairie remaining in North America.
What Did We Do?
Kansas Department of Health and Environment wrote the plan, but embraced those involved with the issue, including K-State Research and Extension, the KS Livestock Association, Farm Bureau, Tallgrass Legacy Alliance, KS Prescribed Fire Council, Cities of Wichita and Kansas City, Natural Resource Conservation Service, KS Dept. of Wildlife Parks & Tourism to develop a plan that would address the goals of all those involved. A website was developed to give ranchers day by day information regarding smoke emission and direction from a prescribed fire that day or the following day.
What Have We Learned?
Those that practice prescribed fire in the Kansas Flint Hills respect the health and environment of their city neighbors. Conversely, those living in neighboring metropolitan areas understand the economic importance of prescribed fire as related to beef cattle production, and the role fire plays in preserving the integrity of the tallgrass prairie. By engaging all entities involved, agreements can be reached, solutions can be found and advancements can be made.
Prescribed fire controls woody species, maintaining the integrity of the tallgrass prairie.
In the years ahead, KS Dept of Health and Environment will continue monitoring smoke emissions due to prescribed fire in the Flint Hills. Those practicing prescribed fire will be encouraged to use the best smoke management methods of prescribed fire. This will be done through K-State Research & Extension prescribed fire schools, the KS Prescribed Fire Council workshops and the KDHE website.
Jeff Davidson K-State Research & Extension Watershed Specialist Kansas State University firstname.lastname@example.org
K-State Research & Extension, Kansas Precribed Fire Council, Kansas Livestock Association, KS Dept. of Health & Environment, Tallgrass Legacy Alliance, KS Dept. of Wildlife, Parks & Tourism, Natural Resource Conservation Service, Farm Bureau, Cities of Wichita and Kansas City.
The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2013. Title of presentation. Waste to Worth: Spreading Science and Solutions. Denver, CO. April 1-5, 2013. URL of this page. Accessed on: today’s date.
There are many methods and options that can be utilized to manage smoke from a prescribed fire.
To minimize smoke problems:
- burn smaller units;
- burn when weather conditions are likely to produce the best dispersion;
- burn when fuel conditions are likely to produce the least amount of smoke;
- utilize suitable ignition techniques for smoke management;
- conduct post-burn mop-up to reduce nuisance smoke;
- reduce the amount of fuels to reduce smoke emissions; and
- reduce the impact of smoke on people.
The National Weather Service fire weather forecasts are a good source of information for smoke dispersion conditions.
For more information see Smoke Management for Prescribed Burns.