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Machine Safety Category Ratings You Should Know – Don’t Get Caught Without Them!

The Department of Labor’s Occupational Safety and Health Administration (OSHA) has set certain standards for various industries to ensure that workers are able to operate machinery safely. These standards are called machine safety category ratings, and they are designed to help protect workers from injury and death.

Most machinery falls into four Machine Safety Category Ratings-

Here are the machinery safety categories:

  • Machine Safety Category 1
  • Machine Safety Category 2
  • Machine Safety Category 3
  • Machine Safety Category 4.

Example – Category 1 machinery includes potentially hazardous machines such as bulldozers, front-end loaders, mechanical shovels, forklifts, cranes, and tractors with four or more wheels.

What are Category Ratings?

Most machines are assigned one of four category ratings: Cat I, Cat II, Cat III or Cat IV. These ratings refer to safety performance levels and help you determine how safe a machine is for an operator. As an example, below is a safety performance level chart that you can use to help quickly determine your machine’s safety category.



These categories play an important role in determining how effective your machine guarding will be—if it is done right. For example, if you do not have machine guards that meet your machine’s safety category rating, then they will not work as well as they should. And if they do not work as well as they should, then there could be serious consequences for workers who operate them.

For example, if you have a Cat II machine that is protected by guards meant for a Cat I or Cat III machine, those guards might not prevent an operator from getting injured if there’s an accident. The safety rating of your machine should be just as important as its energy rating—especially if you want to ensure your employees do not get hurt on it.

If you are not sure what category rating your machine has, you need to do some research. One place to start is by calling your machine manufacturer and asking them. This is usually a free service they offer customers, so you don’t have anything to lose. If they cannot answer your question directly, then it might be worth paying for a professional safety audit to help ensure your machines are properly rated and guarded.


Types of Categories

Safety Performance Level Chart:



A safety performance level chart is a rating system that uses letters to indicate how safe a machine is. The safety category rating or performance level tells you what types of hazards are involved in operating a machine and how likely it is that someone will be injured. This category rating can help you determine whether your business needs to train employees on using certain machines or take additional precautions when operating them.

For example, if you are working with a machine that has an S4 safety rating, it means there are some serious risks associated with its use, so training may be required for anyone who operates it. Some common examples of safety ratings include: S1 – Minimal risk; S2 – Moderate risk; S3 – High risk; and S4 – Serious risk.

The higher a machine’s safety rating, typically, the safer it is to operate. The lowest level of safety category (S1) indicates that there are no serious risks associated with its use, while an S4 indicates that there are significant risks.

In addition to knowing what kinds of risks are involved with certain machines, it is also important to know where they should be used. The machine’s category rating can indicate whether or not it’s appropriate for certain applications. For example, if you have a low-rated machine that could cause serious injuries if improperly used, you may not want to use it around small children or in places where visitors might come in contact with it.


Who Needs to Know About Category Ratings?

Depending on where you are working, either you or your employer needs to know about safety category ratings. If you are an employee, your company is required by law to make sure that your equipment meets relevant standards and complies with all regulations. If you work in a hazardous industry—petroleum refineries, for example—your employer must also ensure that all machine components are up to date and appropriate for working in these conditions.

If you work in a non-hazardous industry and you are using non-mandatory equipment, it is up to you to make sure your machine is safe. If there’s ever an accident or injury on your machine, you could be held responsible for not ensuring that your equipment was up to standard.

So how do you know if you need category ratings? If any of these situations apply to you, make sure that your equipment meets appropriate safety category ratings.

When Using Non-Mandatory Equipment: If you are using non-mandatory equipment—such as a new piece of non-critical machinery—it’s up to you to ensure it’s safe for use. For example, say there’s a brand new pressure washer on sale at your local hardware store; as it’s not required by law for safety category ratings, you must check its safety before use.

If you are unsure if a piece of equipment meets safety category ratings, ask your supplier or manufacturer—they should have all relevant information on file. If they don’t have an answer, check with your national government or industry body to find out which safety category is applicable.

If your equipment does not meet safety category ratings, do not use it until you have found out what needs to be done to update it. If there are no safety category ratings on file for your machine, consult with a professional engineer to find out what changes need to be made and ensure that they comply with all relevant regulations.

READ: What is safety integrity level (SIL)

If you work in a hazardous industry and you are using mandatory equipment, your employer should have safety category ratings in place for all machinery.

If you are required to use a piece of equipment that does not meet category ratings—for example, because it has not been upgraded in over 10 years—it must be clearly marked as non-compliant. Your employer must also provide evidence that demonstrates why they can still use these pieces of machinery.


Machines in the Same Class



Typically, machines with similar safety category ratings can be used interchangeably on similar jobs. For example, a machine with a Cat 3 rating might be able to be used in place of another machine in that same category. But always make sure you talk to your equipment dealer about specific scenarios before making substitutions.

But as you are filling out your purchase order, make sure to also specify a performance level. This helps ensure that you are comparing apples to apples and not apples to oranges (or in our case, Cat 3 machines to Cat 4 machines). In other words, when ordering similar types of machines, it’s important to specify not only safety category ratings but also performance levels.

Note that if you have Cat 4 machines and want to upgrade, you will need to install safety upgrades. Also note that if your budget is limited, you can always buy a less-expensive machine with a lower safety category rating as long as it’s in a similar class (Cat 2 or 3) to your old machine.

All that said, it’s also a good idea to contact your equipment dealer or machine manufacturer and talk about how machines in similar categories should be rated for performance level (and why) before you make any substitutions. That way, you will have as much information as possible when making an informed purchase decision.


Using Machines Safely with Category Ratings

Underwriters Laboratories, Inc. (UL) and Standards Canada have partnered together to create ANSI/UL 498. UL 498 is a safety standard for North American manufacturers on proper usage of their equipment. It goes beyond what OSHA requires in an effort to prevent accidents and injuries. Here are some important ratings you should know when operating machinery: Safety category vs performance level. OSHA safety training is required before using any machines but it is not enough by itself. The safety category rating gives you additional information about how safe a machine is to use and how well it will perform its intended task.

The safety category rating can be found on every machine’s data plate or nameplate. Safety categories range from I-IV with I being least safe and IV being most safe. This information along with the performance level rating gives you all the info needed to operate your machine safely without jeopardizing yourself or others around you.

READ: What is Safety Instrumented System

The performance level of a machine is rated from 1-5 with 5 being best. The performance level is an indicator of how well a machine will perform its intended task or function. A higher rating gives you more confidence that you are getting what you are paying for.

Think of safety category vs performance level as your personal cheat sheet to using machines safely. By understanding both, you will have an informed decision about how to approach each machine you operate. With careful planning and attention to detail, you can use machinery without hurting yourself or others around you.


External Resources

Decoding Ranking Systems Related to Industrial Safety

Safety Components

What’s the difference between PL and SIL machine safety standards?

Decoding Machine Safety

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