These guidelines are to be used by forest landowners, land managers, and fire department personnel in Larimer County in planning and conducting safe and effective forest slash burning in woodland situations. It cannot guarantee safety from accidents, unforeseen circumstances, changing burning conditions, or negligent actions of the individual(s) burning slash. By following the intent of these guidelines and common sense, the landowner or forest manager can reduce forest slash accumulations, improve the appearance of their forest land, and reduce wildfire risk on their properties.


The accumulation of limbs, tops, and miscellaneous residue left by forest management activities, such as thinning, pruning, and timber harvesting.

Piling and burning
The treatment of slash by piling the limbs and tops into manageable piles. Piles are burned during safe burning conditions, generally during the winter following cutting.

Broadcast burning
The treatment of slash by burning the limbs and tops as they lie on the ground after cutting. The slash must be distributed continuously throughout the burn area to be burned effectively. Burning is generally done during very wet periods or with light snow cover in late fall or early spring.

The final check of the burned slash to identify and extinguish still burning coals or materials. Extinguishment is usually accomplished by covering and mixing snow, water, or soil with the burning fuels.

Construction of Piles
Pile slash immediately after cutting (while still green), and before winter snowfall. Remove all wood products such as firewood prior to piling. Pile branches and tops with the butt ends towards the outside of the pile, and overlapping so as to form a series of dense layers piled upon each other. Use a mixture of sizes and fuels throughout the pile. This prevents snow from filtering into the pile and extinguishing the fire while it is starting. Piles should be approximately 8 feet across in diameter and 6 feet in height, again to prevent drifting snow from entering the pile. Piles should be kept compact, with no long extensions, to reduce snow filtration and improve ignition. Do not place large stumps and sections of logs in the piles, as they will burn for extended periods and will frequently need to be mopped-up.

Do not include garbage or debris in the pile. Locate piles in meadows, rock outcrops, or openings in forest stands. Do not pile slash over stumps where possible, as these areas will also need to be mopped-up. Piles may be situated within forest stands, if they are at least 5 feet away from adjacent tree trunks and tree crowns do not hang over the piles.

Planning Your Burning Effort

Landowners must complete the following steps before burning slash:

  1. Obtain and complete a general open burning permit from the Larimer County Department of Health and Environment, 1525 Blue Spruce Dr., Fort Collins, 80524, (970) 498-6775. The Health Dept. will review application and approve/disapprove permit and forward to the fire authority where the property is located for their approval.

  2. Signed authorization and approval from the legally constituted Fire Protection District for your area, or from the Larimer County Sheriff's Department, Office of Emergency Services located at 1303 N. Shields St., Ft. Collins. (970) 498-5300, 498-5302 or 498-5303.

Open burn permits consist of 3 copies, and require the completion of information about the proposed burning. Upon completion of the permit and approval of the Health Department, approval from the responsible fire authorities is required. Upon their approval, the white copy of the permit is returned to the landowner, the yellow copy is retained by the responsible fire jurisdiction, and the pink copy is returned to the Health Department.

The landowner must notify the responsible fire protection agency the day burning is planned. Notification of the Larimer County Sheriff's Department, at (970) 416-1985, is also mandatory and should include the dates, times, and an exact legal description of the burn location. Neighbors should be informed prior to burning as well.

Burning must be done during suitable weather conditions. Periods of snow or light rain, with light winds (for smoke dispersal) and a minimum of 3 inches of snow cover are ideal. Do not burn during periods of high winds, low humidity or drying conditions, temperature inversions, and lack of snow cover or when these conditions are expected to develop after starting. Control of burning slash must be maintained at all times to reduce wildfire hazard and damage to residual trees. If snow cover becomes sparse during the burning period, additional water sources must be provided for wildfire control and mopping-up efforts. Persons conducting the burning should have at a minimum; leather gloves; shovels and mattocks; leather work boots; work clothing; masks or bandannas for covering the mouth and nose; and proper eye protection.

Burning Slash Piles

Piles may be ignited by several means. If the needles and fine fuels within the pile have dried out throughout the summer, then ignition can be easily started with a large ball of newspaper placed within the bottom of the pile. If fuels are still partially green , or the pile is wet from rain or melting snow, then a hotter and longer burning source may be necessary. Sawdust, saturated with diesel fuel and placed within the bottom of the pile, can be used. Flares used for highway emergencies can also be utilized to ignite the piles. Do not use gasoline for this purpose!

One pile should be burned first as a test pile to see how it burns and at what rate prior to igniting other piles. If suitable burning conditions exist, then additional piles may be started. Ignite only those piles that can be watched with the available manpower until the piles have burned down. Depending on weather conditions, pile size, and moisture content of the fuels, piles should burn down in 20 to 35 minutes. As a general rule, 3 to 6 piles per person is a manageable rate if piles are closely situated.

After the piles have burned down, re-pile any unburned slash and large wood chunks (called "chunking-in") into the beds of coals before starting any new groups of piles. Do not start any new piles after 2:00 p.m. Piles started after this time may continue to burn into the evening.

If landowners have questions about possible problems with burning slash, they should contact the Larimer County Sheriff's Department, Office of Emergency Services at 498-5300, 498-5301 or the Colorado State Forest Service, Fort Collins District Office at 491-8660. Information about wildfire hazard reduction for forest land is available form the Fort Collins District, CSFS at 491-8660.

Air Quality

Department of Health and Environment - Environmental Health