Short answer
AQL is not a quality level. It is an acceptance threshold applied to a sample, and it only protects you if you define which defects count as critical, major and minor for your product.
Under ANSI/ASQ Z1.4 at general inspection level II, a lot of 1,201 to 3,200 units draws code letter K, which is a 125-piece sample. At AQL 2.5 that plan accepts the lot with up to 7 defects and rejects at 8. Those numbers come from the standard's master table, not from the inspection company, so you can verify any report against them.
For massage devices the decisive choice is not the AQL number. It is whether the checklist includes a powered function test on every sampled unit, and a temperature measurement on every heated unit.
How the sampling plan is actually derived
Two tables produce the plan. The first maps lot size and inspection level to a sample size code letter. The second maps that letter and your AQL to a sample size with accept and reject numbers.
Level II is the normal default. Level I uses smaller samples and is cheaper but weaker; level III uses larger samples for tighter control. If your supplier or inspector proposes level I without saying so, your effective protection drops while the AQL number on the report stays the same.
| Lot size | Code letter (level II) | Sample size | Accept / reject at AQL 2.5 |
|---|---|---|---|
| 151 to 280 | G | 32 | 2 / 3 |
| 281 to 500 | H | 50 | 3 / 4 |
| 501 to 1,200 | J | 80 | 5 / 6 |
| 1,201 to 3,200 | K | 125 | 7 / 8 |
| 3,201 to 10,000 | L | 200 | 10 / 11 |
| 10,001 to 35,000 | M | 315 | 14 / 15 |
Defect classification for massage devices
This is the part buyers delegate and then regret. A general consumer-goods checklist treats defects cosmetically, which is appropriate for a handbag and inadequate for a heated device with a lithium cell.
Classify by consequence. Anything that can injure a user or cause a fire is critical and should carry a zero-tolerance position regardless of the AQL applied to cosmetic defects. Anything that stops the product performing its advertised function is major. Finish issues that a customer would notice but that do not affect function or safety are minor.
- Critical: exposed live conductor, battery swelling or leakage, overheating beyond the specified maximum, missing or incorrect safety marking
- Critical: heating element reaching a temperature above the declared limit, or temperature control failing to cut off
- Major: motor fails to start, a mode or speed level inoperative, heat function inoperative, charging failure, auto-off timer not working
- Major: accessory missing from the set, wrong adapter or wrong plug type for the destination market
- Minor: surface scratch within an agreed size limit, slight colour variation against the approved sample, minor printing misalignment on the colour box
Function tests to specify explicitly
An inspector will only perform the tests on your checklist. For our product range the following are worth naming individually, because each one maps to a genuine return cause rather than to a theoretical risk.
Where a product declares a temperature, require a measurement rather than a touch test. A heated lumbar belt with five temperature levels and a heated ankle unit adjustable from 40 to 60 degrees Celsius both need the top level verified against the specification with an instrument.
- Power on every sampled unit and cycle through every mode and speed level
- Measure the maximum surface temperature on heated models against the declared limit
- Charge and discharge a subset to confirm stated runtime, not merely that charging begins
- Verify the auto-off timer actually cuts power at the stated interval
- Confirm the adapter plug type and voltage range match the destination market
- Confirm manual language and warning text match what you approved
- Check carton count, gross weight and shipping marks against the packing list
- Confirm battery state of charge at packing if the consignment moves by air
Where buyers lose money on inspection
The common failure is timing. A pre-shipment inspection on a finished, packed lot leaves you with two choices if it fails: accept with a concession, or delay the shipment. Neither is good when a retail window is fixed.
During-production inspection at roughly 20 to 30 percent completion costs the same and preserves the option to correct. For a first order with a new supplier, or any order with new tooling, that timing is worth more than a tighter AQL on a finished lot.
How we work with your inspector
We expect third-party inspection and we would rather align the checklist before production than argue about interpretation afterwards. Send us your defect classification and function test list with the order, and we will confirm what is measurable on our line.
Our range is covered by FDA, UL, CE, RoHS, UKCA, KC and ISO 9001 certification, and each model's declared electrical and dimensional data is published on its product page so your inspector has a specification to measure against rather than an impression to form.
Frequently asked questions
What AQL should I use for massage devices?
A common commercial position is AQL 2.5 for major defects and 4.0 for minor, with zero tolerance for critical defects. What matters more than the number is your defect classification: for a heated or battery-powered device, electrical and thermal failures belong in the critical class rather than being counted against a 2.5 threshold.
How many units will be inspected?
It depends on lot size and inspection level. At general inspection level II under ANSI/ASQ Z1.4, a lot of 1,201 to 3,200 units draws code letter K and a 125-piece sample, accepting at 7 defects and rejecting at 8 under AQL 2.5. A 3,201 to 10,000 lot draws letter L and a 200-piece sample. Confirm the level, because level I uses smaller samples.
Does a passed AQL inspection mean there are no defects?
No. Sampling accepts a lot when defects in the sample stay at or below the acceptance number, so a passed lot can still contain defects. That is why critical safety defects should be handled on a zero-tolerance basis rather than being folded into a statistical threshold.
Should I inspect during production or before shipment?
During production, at roughly 20 to 30 percent completion, for a first order or any order with new tooling. It costs the same as a pre-shipment inspection but leaves time to correct a systematic fault. Pre-shipment inspection is appropriate for repeat orders on a stable line.
Can we send our own inspector or inspection company?
Yes, and we recommend it. Send the defect classification and function test checklist with the order so we can confirm in advance what is measurable on our line. Aligning the checklist before production prevents disputes over interpretation at the end.
Sources
- ANSI/ASQ Z1.4 single sampling plan for normal inspection (AQL chart) — Z1.4-2003 tables
- ASQ — guidance on Z1.4 inspection levels — 24 May 2012
- IATA Dangerous Goods Regulations, 67th edition (state of charge) — Applies from January 2026
This article is general information, not medical advice. A therapeutic massager is intended to relieve minor muscle aches and pains; it does not diagnose, treat, cure or prevent any disease. Consult a qualified healthcare professional about your individual circumstances.