AQL Inspection Levels: What are They? How do You Use Them?

by | Aug 4, 2021 | AQL, Product Inspections, Quality Control, Video

Once you’ve decided to conduct third-party product inspections, it is vital to get a clear understanding of how AQL sampling works.

If you want to work more effectively with your QC services provider and achieve excellent product quality, your knowledge of this inspection standard will help you avoid headaches and confusion down the road. So it’s great that you’re taking the time to learn about the Inspection Levels!

When you look at the AQL chart, you can see four Special Inspection Levels and three General Inspection Levels (seven in total) at the top. But what is the difference between them, and how do you use them in your inspections? Read on to learn more.

AQL Inspection Levels on the AQL chart

What’s the Difference Between the Special and General Inspection Levels?

AQL Inspection Levels - General and Special Levels

Keep in mind that the inspection levels help you determine your sample size. The primary difference between them is that the General Levels will give you a larger sample size while the Special Levels will give you a smaller sample size.

Additionally, when your inspector goes to the factory, your quality inspection checklist will serve as their guide. The checklist has a multitude of different tests and checks for them to conduct. The crucial point here is that they will use one of the General levels (e.g., Level II) for most of the tests while using the Special levels (e.g., S-4) for some others.

Mobile Phone Inspection Checklist

For example, let’s say you’ve ordered a shipment of 5,000 mobile phones and contracted Insight to conduct product inspections at your factory. One item on your checklist (B1 below) is a visual inspection of the units — checking the material, workmanship, sizes, colors, and texture of the phones.

We might use General Level II for this check, which means the inspector would visually inspect 200 phones.

Checklist Item with General Level II sampling

Another test requires the inspector to power each phone on and off to check that the phone vibrates. We could use Special Level S-4 for this test so that the inspector would only power 32 phones on and off.

Checklist item at Special Level S-4

If you are unsure of how we arrived at the numbers above, download our AQL 101 guide. It will give you a high-level overview of the sampling method and show you how to use the chart. But how do you use the General Levels and choose the right one?

The 3 General Inspection Levels: How to Use Them

The AQL General Levels

The three General Inspection Levels apply to the inspection broadly. They are General Level I, II, and III. After you select one, the inspector will use it to conduct most of the tests on your checklist. So which one should you pick?

You can choose General Level II as your default level for AQL inspections. Consider it your starting point, and under certain circumstances, you can drop down to Level I or move up to Level III. For example, you can:

  • Use General I to inspect fewer units. If you have been working with the factory for a considerable time and they have earned your trust, this may be appropriate.
  • Use General III to inspect more units. If you are working with a brand new supplier or one that has had quality problems, this may be appropriate.

To learn more about how this works, read our article about the three AQL General Inspection Levels. But what about the Special Levels?

The 4 Special Inspection Levels: How to Use Them

AQL Special Inspection Levels

The AQL chart includes four Special Inspection Levels — S-1, S-2, S-3, and S-4. Using S-1 leads to the smallest sample size, while S-4 leads to the largest sample size among the Special Levels. But all four levels lead to smaller sample sizes than the General Levels.

While the General Levels apply to the inspection broadly, the Special Levels apply only to specific tests. These levels are used for tests that may be destructive to the item being checked, expensive or time-consuming to conduct, or tend to yield similar results across all items in the lot.

For more information about this, read our article on the AQL Special Inspection Levels.


The AQL chart offers guidelines on the number of samples to be inspected across the three General and four Special Inspection Levels. When conducting an inspection, you will choose one General Level that applies to the inspection as a whole. For specific tests on your checklist, you can use Special Levels if appropriate.

If you have any questions about your specific situation, you can reach out to us to discuss. Or, if you’d like to gain a better understanding of AQL sampling, download our AQL 101 guide.

Free White Paper: AQL Inspections 101

As a consumer goods importer, the quality of your products is key to your success. And when you’re conducting product quality inspections, the AQL standard determines your sample size. Having a good grasp of this method allows you to work with your third-party inspectors more effectively. This white paper will teach you all the basics of the AQL method.

Thanks for reading! Do you have any questions about the article? Is there something else you’d like to add? Leave a comment below and we will get back to you.

Andy Church

Founder & CEO, Insight Quality Services


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