When planning an attack on a fire, the length and width of the line must be estimated, along with the capabilities of the hand crew(s), to determine how many crews will be needed. Generally, a 15-person crew should be able to construct a 3-foot fireline around a 1-acre grass fire in 1 hour. Below are some average ideal rates for hand crew production rates in various vegetation.

Hand crews primarily construct fireline but can also assist on hose lays, firing operations, protecting structures, mopping up, cleaning up, and other logistical support functions. It is important to match the task to crew capabilities. Use the best, most experienced crews for the toughest jobs and the hottest firelines. Crew effectiveness is controlled by these factors:

Standard deviation, or variance, is a measure of the closeness of each term to the average (mean). If the terms are all close to the mean or average, then the standard deviation will be small and the mean can be considered an accurate approximation of the distribution.

The deviation of a set of numbers is the difference between the average and the individual terms.

Example 1 - Jane paces off the following fire run lengths. Find the deviation of the fire run lengths, given as 6.5, 6.0, 8.0, and 7.5 chains.

Step 1. Calculate the average (see Section 9.3). Sum the numbers and divide by the number of individual elements: 28/4 = 7.0 

Step 2. Now, subtract each term from the average.
6.5 - 7.0 = -0.5
6.0 - 7.0 = -1
8.0 - 7.0 = 1.0 

Range refers to the difference between the smallest number and the largest number possible for a given quantity.

Example 1 - Philip paces off some fire run distances and gets the following values in chains: 7.5, 6.0, 8.5, 5.5, 9.0. Find the range for the measurements.

Step 1. Arrange the numbers in ascending order (from the smallest to the largest).
5.5, 6.0, 7.5, 8.5, 9.0 

Step 2. Subtract the largest number from the smallest number.
9.0 - 5.5 = 3.5

The average, or the mean, is the sum of all the numbers divided by the number of terms.

Example 1 - The line production rates for the members of a hand crew were as follows: 8.0 chains per hour, 7.0 chains per hour, 6.0 chains per hour, 7.5 chains per hour, and 7.0 chains per hour. What is the average number of fireline chains constructed per hour?

Step 1. Add all the numbers.
8.0 + 7.0 + 6.0 + 7.5 + 7.0 = 35.5 chains

Step 2. Count the number of terms.
5 terms

Probability is the chance that an event will happen and is expressed in terms of percent, or per 100. For example, if there is a 40 percent chance of a spot fire starting, that means that out of 100 glowing embers that fly off, 40 embers will likely start spot fires, and 60 will not. Percent is calculated by changing the percent into a fraction by dividing by 100, then multiplying by the total number of possible situations.

Example 1 - The probability of ignition is 80 percent. How many ignitions are likely to occur if 90 glowing firebrands land on receptive fuel?

When fire moves upslope, the fuel ahead of the flame front is closer to the flame than if the slope were flatter.  This set-up "preheats" the fuels. The effects of slope on fire spread become greater as the slope increases.