Clemson Extension Forestry and Wildlife

The Safety Features of a Modern Chainsaw

Now that the outside temperatures are cooling down, it is a great time to start working on cutting some firewood for next year or cleaning up some of those trees that the summer storms knocked over. Many of you have probably used chainsaws for years or decades and are well-versed in the use of them. But do you know about the safety features of modern chainsaws and whether your chainsaw has them?

Modern chainsaws, meaning chainsaws produced after the mid-1980s, all have four distinct chainsaw safety features (chain brake, inertia brake, throttle trigger lockout, and chain catch pin) that are designed to keep you as the user safe and minimize major injuries. The chain brake (Figure 1) is part of the front handguard in front of the upper handle facing the saw chain. The function is simple, when engaged (pushing the hand guard towards the saw chain), the chain brake will prevent the saw chain from spinning, no matter how hard you pull the throttle trigger. When disengaged (pulling the hand guard towards you away from the saw chain), it will release the saw chain and allow it to spin again. The best way to use the chain brake is to engage it every time you have completed a cut and are ready to take a few steps to the next cutting spot. This will greatly reduce the risk of accidental cuts when moving around. The inertia brake is designed to engage the chain brake when a large rotational force is applied to the chainsaw. This mostly happens in the case of kickback, the fast movement of the chainsaw toward the user when the top corner of the saw chain catches on some branches or other hard material. However, any fast movement that produces a large force will trigger the inertia brake. This is designed to keep the user of the chainsaw safe by stopping the saw chain from spinning and potentially cutting the user.

The throttle trigger lockout (Figure 1) is another safety feature that is designed to keep your right hand out of harm’s way and to ensure a safe grip on the chainsaw. At the back of the chainsaw where the trigger is, you will find that you cannot depress the trigger unless you also depress another little button or tab that is either on top of the rear handle or with many battery-powered chainsaws, on the side of the rear handle. Properly depressing the lockout button will require you to firmly wrap your right hand around the rear handle. This also provides you with a lot of control when handling the chainsaw. This is an important safety feature, so do not tape the throttle trigger lockout button to the handle or otherwise permanently engage it.

The chain catch pin (Figure 1) as the name suggests is a pin at the bottom of the chainsaw near the front of the power head where the saw chain comes into the clutch cover. In case the saw chain comes off the guide bar, the still rotating saw chain will drop and catch on the chain catch pin where most of the energy of the saw chain will be absorbed. After that, the saw chain will likely swing upwards and hit the underside of the rear handle, the rear chain breakage guard, before all energy from the saw chain is expended. All of this happens within a second or so, and while the loud bang of the saw chain hitting the rear handle can be shocking, the combination of the chain catch pin and rear handle will keep you safe and prevent major injuries. Once this happens, your chain catch pin will be damaged and you should replace it to ensure safe working conditions of your chainsaw. Most chain catch pins are secured with one screw to the chainsaw and can easily be replaced by yourself or a service technician.

While not a safety feature to protect yourself, the spark arrestor keeps any sparks from the engine exhaust system and muffler contained and as such prevents accidental forest fires. The spark arrestor comes in a variety of different forms but most often you can find a mesh screen over the muffler exhaust openings. Another form of spark arrestor is a metal cover over the muffler with an exhaust opening at the sides This will catch any sparks coming straight out of the engine and divert the exhaust gases to the side. You can find the spark arrestor and muffler at the front of the chainsaw right above the saw chain and guide bar. It is good practice to periodically check the spar arrestor to make sure that it is not damaged or clogged up with debris or sap.

This was a brief overview of the safety features that exist on modern chainsaws. Make sure all these safety features are in working condition with your chainsaw and replace broken parts before using the chainsaw. For more details on chainsaw safety and handing see the Land-Grant Press by Clemson Extension article by Patrick Hiesl and Janet Steele ( and watch out for the next article on chainsaw safety and personal protective equipment in the CU in the Woods newsletter.

Chainsaw with arrows and labels pointing to the safety features.
Figure 1: Chainsaw safety features and other components of a chainsaw. Photo Credit: Patrick Hiesl, Clemson University. In “How to Stay Safe Around Chainsaws”, Land-Grant Press by Clemson Extension, 2022.


Patrick Hiesl, Clemson University, Associate Professor of Forest Operations

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