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2.1 Unit Conversion and Conversion Factors

UNIT CONVERSION AND CONVERSION FACTORS

A unit conversion expresses the same property as a different unit of measurement. For instance, time can be expressed in minutes instead of hours, while distance can be converted from miles to kilometers, or feet, or any other measure of length. Often measurements are given in one set of units, such as feet, but are needed in different units, such as chains. A conversion factor is a numeric expression that enables feet to be changed to chains as an equal exchange. 

A conversion factor is a number used to change one set of units to another, by multiplying or dividing. When a conversion is necessary, the appropriate conversion factor to an equal value must be used. For example, to convert inches to feet, the appropriate conversion value is 12 inches equal 1 foot. To convert minutes to hours, the appropriate conversion value is 60 minutes equal 1 hour.

A unit cancellation table is developed by using known units, conversion factors, and the fact that a unit of measure ÷ the same unit of measure cancels out that unit. The table is set up so all the units cancel except for the unit desired. To cancel a unit, the same unit must be in the numerator and in the denominator. When you multiply across the table, the top number will be divided by the bottom number, and the result will be the answer in the desired units.

Example 1 - Ralph wants to know how many seconds are in 3 hours and 36 minutes. 

Step 1. Change 3 hours and 36 minutes to the same units. This unit can be hours or minutes. Using minutes is easier because the end time value will need to be in seconds.

The appropriate conversion factor is: 1 hour = 60 minutes.

Conversion Factor

3 hours and 36 minutes = 180 minutes plus 36 minutes = 216 minutes

Step 2. Set up the cancellation table so all units will cancel, except the desired unit, seconds.

The appropriate conversion factor is:
1 minute = 60 seconds.

1 minute = 60 seconds converstion

There are 12,960 seconds in 3 hours 36 minutes.

Notice that the hour units on the top and bottom cancel along with the minutes, leaving seconds as the only unit.

Setting up a unit cancellation table helps keep units straight, even for the most seasoned professional firefighter. These tables are particularly important when more than one unit conversion is necessary to obtain the desired unit. Answers should always be presented with the appropriate number of significant digits. For information about significant digits and rounding, please review Section 1.6, Using Decimals.

Example 2 - How many pints are in a 5-gallon pail? How many cups are in a 5-gallon pail?

Step 1. Find the appropriate conversion factors in Table 2.1 at the end of this chapter.
1 gallon = 4 quarts, 1 quart = 2 pints, 1 pint = 2 cups

Step 2. Set up the cancellation table so all units will cancel, except the desired unit, pints.

Gallons to Pints

There are 40 pints in 5 gallons.

Pints to Cups

There are 80 cups in 5 gallons.

Example 3 - Javier constructed 2,678 feet of dozer line. How many chains of dozer line did he construct?

Step 1. Find the appropriate conversion factor in Table 2.1. 1 chain = 66 feet

Step 2. Set up the cancellation table so all units will cancel, except the desired unit, chains.
 

Feets to Chains

Javier constructed 41 chains of dozer line.

Notice that Table 2.2 has two conversions for each set of units. When setting up the cancellation table, it is not important which conversion factor is used. What is important is that the appropriate units cancel so that the correct end result is achieved. 

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Updated NWCG Standards for Water Scooping Operations, PMS 518

Date: December 19, 2024
Contact: Water Scooper Operations Unit

The NWCG Standards for Water Scooping Operations, PMS 518 establishes the standards for dispatching, utilizing, and coordinating water scooping aircraft on interagency wildland fires. These standards should be used in conjunction with the NWCG Standards for Aerial Supervision (SAS), PMS 505, and any local, state, or geographic/regional water scooping plans.

References:

NWCG Standards for Water Scooping Operations, PMS 518

Updated NWCG Standards for Aerial Supervision, PMS 505

Date: December 19, 2024
Contact: Interagency Aerial Supervision Subcommittee

The Interagency Aerial Supervision Subcommittee has updated the NWCG Standards for Aerial Supervision, PMS 505. PMS 505 establishes standards for aerial supervision operations for national interagency wildland fire operations. 

References:

NWCG Standards for Aerial Supervision, PMS 505

New Job Aids Available: Packing Lists for Wildland Fire Fireline Personnel and Support Staff, J-101 and J-102

Date: December 3, 2024
Contact: NWCG TRAINING

Two new job aids are now available: Packing List for Wildland Fire Fireline Personnel, J-101 and Packing List for Wildland Fire Support Personnel, J-102, should serve as a baseline for items needed on a wildland fire assignment. These lists will help personnel prepare for a 14 to 21-day assignment on the fireline or in a support role.

References:

Job Aid Catalog

NWCG Packing List for Wildland Fire Fireline Personnel, J-101

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NWCG Equipment Technology Committee Releases Safety Warning: 24-001 Stihl Chainsaw Toolless Fuel Cap Spill Prevention

Date: November 14, 2024
Contact: Equipment Technology Committee

The Equipment Technology Committee (ETC) has released Safety Warning: 24-001 Stihl Chainsaw Toolless Fuel Cap Spill Prevention. Misaligned toolless fuel caps on Stihl chainsaws have led to recurring fuel spillage, fuel ignition, and burn injuries during wildland fire management operations.

This Safety Warning is intended to highlight the details and recommended procedures for the installation of a Stihl chainsaw toolless fuel cap, as well as how to identify and correct a misaligned, damaged, or broken fuel cap to help prevent fuel spillage.

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NWCG Safety Warning: 24-001 Stihl Chainsaw Toolless Fuel Cap Spill Prevention

Advertencia de equipos 24-001: Prevención de derrames de la tapa de combustible sin herramientas de la motosierra Stihl

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