Quality Control & Product Inspection Glossary

What is AQL (Acceptable Quality Level)?

AQL (Acceptable Quality Level) is a statistical quality control standard defined in ISO 2859-1 that determines the maximum acceptable number of defective units in a random sample from a production lot. AQL does not measure the actual defect rate of an order — it defines the threshold at which a lot is accepted or rejected based on sampling. The most commonly used AQL levels in consumer goods inspection are 0.0 for critical defects (safety hazards), 1.0 for major defects (functional failures), and 2.5 for minor defects (cosmetic imperfections). AQL sampling plans specify three parameters: the lot size, the inspection level (General Inspection Level II is standard), and the AQL value. Together, these determine the sample size and the accept/reject number. AQL-based inspection is the global standard used by importers, retailers, and third-party inspection companies including Tetra Inspection to make objective, statistically valid pass/fail decisions on production lots before shipment.

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What is PSI (Pre-Shipment Inspection)?

A Pre-Shipment Inspection (PSI) is a quality control check performed when 80–100% of an order is finished, packed, and ready for shipment. PSI is the most widely used type of third-party product inspection in international trade. During a PSI, an inspector visits the factory, draws a random sample from the finished goods using AQL-based sampling plans (typically ISO 2859-1, General Inspection Level II), and evaluates the sample against the buyer's specifications, approved samples, and applicable standards. The inspection covers workmanship, functionality, dimensions, labeling, packaging, and barcode scannability. A detailed report with 100+ photos is delivered within 24 hours. PSI acts as the final quality gate before goods leave the factory — once products are shipped, the cost and complexity of addressing defects increases dramatically. Tetra Inspection conducts pre-shipment inspections in 45+ countries starting at $240 per man-day (Tetra Inspection pricing data, Q1 2026).

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What is DPI (During Production Inspection)?

A During Production Inspection (DPI) — also called an in-process inspection or DUPRO — is a quality control check performed when approximately 20–60% of the order quantity has been completed. The purpose of a DPI is to identify quality issues, specification deviations, or process problems while production is still underway, when corrective action is most effective and least expensive. The inspector examines finished units from early production runs using AQL sampling, reviews work-in-progress on the production line, checks raw materials and components still to be used, and assesses the factory's adherence to the agreed production schedule. DPI is particularly valuable for large orders, new products, new suppliers, and orders with tight delivery deadlines, because it provides early visibility into quality trends before the entire lot is completed. If problems are found, the factory has time to implement corrections for the remaining production.

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What is IPC (Initial Production Check)?

An Initial Production Check (IPC) — also called a first article inspection or early production inspection — is a quality control check performed at the very beginning of production, typically when the first 5–10 finished units have come off the production line. The IPC verifies that the factory has correctly interpreted the buyer's product specifications, is using the approved raw materials and components, has properly calibrated machinery and tooling, and is producing units that match the golden sample. An IPC is the earliest and most cost-effective quality intervention because it catches specification misunderstandings, material substitutions, and setup errors before mass production begins. Without an IPC, such issues may not surface until the pre-shipment inspection when 100% of goods are completed — resulting in expensive rework or reproduction. IPCs are essential for new product launches, first orders with new suppliers, and products with tight tolerances.

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What is CLC (Container Loading Check)?

A Container Loading Check (CLC) — also called a container loading supervision or loading inspection — is a quality control check performed at the factory or warehouse while finished goods are being loaded into a shipping container. The CLC verifies that the correct products, quantities, and packaging are being loaded; that carton markings, shipping marks, and barcodes match the packing list; that goods are properly secured and protected for transit; and that the container itself is clean, dry, structurally sound, and free of contamination or odors. A CLC prevents common shipping problems: short shipments, mixed orders, loading damage, moisture exposure, and container contamination. The inspector also records the container number, seal number, and photographic evidence of the loading process, providing the buyer with a documented chain of custody from factory floor to sealed container.

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What is Factory Audit?

A factory audit is a systematic, on-site evaluation of a manufacturing facility's capabilities, quality management systems, production processes, and compliance with buyer requirements or industry standards. Factory audits are conducted before placing a first order with a new supplier (qualification audit), periodically during an ongoing supplier relationship (surveillance audit), or in response to quality failures (corrective action audit). A comprehensive factory audit evaluates the facility's organizational structure, quality management system (QMS), incoming material controls, in-process quality checks, final inspection procedures, equipment maintenance, worker training, warehouse management, and packaging processes. The audit produces a scored report that rates the factory's overall capability and identifies specific areas of non-conformance requiring corrective action. Factory audits are a foundational element of any supplier quality management program.

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What is ISO 17020?

ISO/IEC 17020 is the international standard that specifies requirements for the competence and impartiality of bodies performing inspection activities. Published by the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC), it defines the organizational, management, and technical requirements that inspection bodies must meet to demonstrate they operate competently, consistently, and impartially. Formal ISO 17020 accreditation is granted by national accreditation bodies, confirms documented inspection procedures, qualified personnel, calibrated equipment, and quality management systems, and is subject to regular surveillance audits. To be clear: Tetra Inspection is not an ISO-17020-accredited body and does not claim accreditation. As an independent third-party inspection company, Tetra applies ISO 17020 inspection principles — competence, independence, and impartiality — across its work, backed by 20,000+ inspections for 2,000+ clients across 45+ countries.

What is ISO 2859-1?

ISO 2859-1, titled "Sampling procedures for inspection by attributes — Part 1: Sampling schemes indexed by acceptable quality limit (AQL) for lot-by-lot inspection," is the international standard that defines the statistical sampling plans used in quality control inspections worldwide. Originally derived from the U.S. military standard MIL-STD-105E, ISO 2859-1 provides tables that specify how many units to inspect (sample size) and how many defects are acceptable (accept/reject numbers) based on the lot size, the inspection level, and the desired AQL. General Inspection Level II is the standard level used for most consumer goods inspections. The standard covers single, double, and multiple sampling plans, as well as switching rules between normal, tightened, and reduced inspection based on recent lot quality history. Virtually every third-party inspection company, including Tetra Inspection, uses ISO 2859-1 as the basis for AQL sampling during pre-shipment and during-production inspections.

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What is SOP (Standard Operating Procedure)?

A Standard Operating Procedure (SOP) in quality control is a documented, step-by-step set of instructions that defines how a specific inspection, test, or audit task should be performed. SOPs ensure that inspections are conducted consistently regardless of which inspector performs them, which factory is being visited, or which country the inspection takes place in. A well-written SOP specifies the inspection scope, required equipment, sampling methodology, test methods, measurement criteria, defect classification guidelines, pass/fail criteria, and reporting requirements. In third-party inspection, buyers often develop custom SOPs that reflect their specific product requirements, quality standards, and regulatory obligations. Tetra Inspection supports custom SOP inspections where clients upload their own checklists and procedures, which are then followed precisely by the assigned inspector, ensuring that every inspection aligns exactly with the buyer's quality expectations.

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What is COC (Certificate of Conformity)?

A Certificate of Conformity (COC) — also called a Certificate of Compliance or Conformance Certificate — is an official document issued by an accredited inspection body or testing laboratory that certifies a product, shipment, or production lot meets specified standards, regulations, or contractual requirements. COCs are required for import clearance in many countries, particularly in the Middle East, Africa, and parts of Asia. The certificate typically states the product description, applicable standard or regulation, test or inspection results, lot identification, and the date and signature of the certifying body. Several countries operate mandatory conformity assessment programs: Saudi Arabia requires SASO/SABER certificates, Kuwait requires KUCAS certificates, and many African nations participate in the PVOC (Pre-shipment Verification of Conformity) scheme. Tetra Inspection performs the physical product inspection and testing against declared standards that underpins conformity documentation, with a track record of 20,000+ inspections across 45+ countries.

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What is SASO (Saudi Standards, Metrology and Quality Organization)?

SASO (Saudi Standards, Metrology and Quality Organization) is the national standards body of Saudi Arabia responsible for developing and enforcing product standards, technical regulations, and conformity assessment procedures for goods imported into or manufactured in the Kingdom. SASO administers the SABER electronic platform, which is the mandatory online system for processing all Certificates of Conformity for products entering Saudi Arabia. Under the SASO conformity assessment scheme, regulated products must undergo testing and inspection by a SASO-recognized body before a Shipment Certificate of Conformity (SCOC) is issued, which is required for customs clearance at Saudi ports. Product categories covered include electronics, building materials, textiles, toys, automotive parts, chemicals, and food products. The requirements and product scope are updated regularly, so exporters to Saudi Arabia should verify current requirements before each shipment.

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What is RoHS (Restriction of Hazardous Substances)?

RoHS (Restriction of Hazardous Substances) is a European Union directive (Directive 2011/65/EU, commonly called RoHS 2) that restricts the use of specific hazardous materials in electrical and electronic equipment (EEE). The directive limits the concentration of six substances — lead (Pb), mercury (Hg), cadmium (Cd), hexavalent chromium (Cr6+), polybrominated biphenyls (PBB), and polybrominated diphenyl ethers (PBDE) — to maximum levels of 0.1% by weight (0.01% for cadmium) in homogeneous materials within EEE. An amendment (EU 2015/863) added four phthalates (DEHP, BBP, DBP, DIBP) to the restricted substances list. RoHS compliance is mandatory for EEE sold in the EU market, and many other countries have adopted similar regulations. During quality control inspections, RoHS compliance is verified through documentation review (test reports from accredited laboratories) and, in some cases, on-site XRF screening of materials.

What is Defect Classification?

Defect classification is the systematic categorization of product defects into severity levels used during quality control inspections to determine whether a production lot passes or fails. The standard three-tier classification system divides defects into critical, major, and minor categories, each with its own AQL threshold. Critical defects are those that could cause injury, safety hazards, or regulatory non-compliance — the typical AQL for critical defects is 0.0, meaning zero critical defects are acceptable. Major defects affect the product's function, performance, salability, or significantly deviate from specifications — the standard AQL for major defects is 2.5. Minor defects are cosmetic or aesthetic imperfections that do not affect function or salability — the standard AQL for minor defects is 4.0. Accurate defect classification requires a clear, product-specific defect list agreed between buyer and inspector before the inspection begins. Tetra Inspection works with clients to develop custom defect classification guidelines tailored to each product category.

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What is Golden Sample?

A golden sample — also called a reference sample, master sample, or approved sample — is a physical product unit that represents the exact quality, appearance, dimensions, materials, and workmanship that the buyer expects from a production order. The golden sample serves as the definitive quality reference during manufacturing and inspection: the factory uses it to set up production, and the inspector uses it to evaluate whether finished units conform to expectations. A proper golden sample should be a production-representative unit (not a hand-made prototype) that has been formally approved by the buyer in writing. During a pre-shipment inspection, the inspector compares randomly sampled units against the golden sample for visual appearance, color, dimensions, material feel, weight, and functional performance. Discrepancies between production units and the golden sample are documented as findings in the inspection report. Providing a clear golden sample is one of the most effective ways to reduce specification disputes between buyers and factories.

What is Third-Party Inspection?

Third-party inspection is an independent quality control service performed by a company that has no financial or commercial relationship with either the buyer or the manufacturer. Unlike first-party inspection (the factory inspecting its own products) or second-party inspection (the buyer inspecting products themselves), third-party inspection provides an unbiased, objective assessment of product quality and compliance. Third-party inspection companies like Tetra Inspection rely on dedicated inspectors who visit factories, draw random samples from production lots, evaluate products against specifications and standards, and deliver detailed inspection reports with photographs and measurements. The independence of third-party inspection is its core value: because the inspection company has no stake in whether the product passes or fails, the results are trustworthy and can be used for commercial decisions, regulatory compliance, and dispute resolution. Third-party inspection is a standard practice in international trade, particularly for goods manufactured in Asia, where geographic distance makes direct buyer oversight impractical.

What is Supplier Verification Audit?

A Supplier Verification Audit (SVA) — also called a supplier assessment, factory assessment, or supplier qualification audit — is an on-site evaluation of a potential or existing supplier's legitimacy, capability, and reliability before placing or continuing production orders. Unlike a full factory audit that evaluates quality management systems in depth, a supplier verification audit focuses on confirming basic facts: Does the factory exist at the declared address? Is it a genuine manufacturer or a trading company? Does it have the machinery and production capacity to fulfill the order? What is the condition of the facility? How many workers are employed? What certifications does the factory hold? The audit helps buyers avoid common sourcing risks such as dealing with middlemen posing as factories, overestimating supplier capacity, or working with facilities that have undisclosed compliance issues. Tetra Inspection delivers supplier verification audit reports within 48 hours across 45+ countries.

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What is Social Compliance Audit?

A social compliance audit is a systematic assessment of a factory's labor practices, working conditions, health and safety standards, and environmental practices against established ethical standards and codes of conduct. Social audits evaluate compliance with international frameworks such as SA 8000, BSCI (amfori), WRAP, SMETA (Sedex), and buyer-specific codes of conduct. Key areas assessed include child labor and young worker protections, forced labor indicators, wages and benefits, working hours and overtime, freedom of association, discrimination, disciplinary practices, health and safety conditions, dormitory conditions, environmental management, and management systems. Social compliance audits are increasingly required by retailers, brands, and e-commerce platforms as part of their responsible sourcing programs. Non-compliance findings are categorized by severity, and factories receive a corrective action plan with deadlines for remediation.

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What is Man-Day?

A man-day is the standard billing unit used by third-party inspection companies to price quality control services. One man-day represents one inspector working for one full day (typically 8 hours) at a single factory location. The man-day rate is an all-inclusive price that covers the inspector's time, travel to the factory, the inspection or audit itself, and the preparation and delivery of the inspection report. Man-day pricing provides transparency and predictability for buyers budgeting their quality control costs. Tetra Inspection's man-day rates start at $240 in Asia and Africa, $340 in Latin America and Turkey, and $440 in Europe — with subscription plans reducing rates to as low as $158 per man-day (Tetra Inspection pricing data, Q1 2026). When comparing inspection companies, buyers should verify what is included in the man-day rate, as some providers charge additional fees for travel, reports, or administrative overhead on top of the base rate.

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What is Inspection Report?

An inspection report is the formal document delivered by a third-party inspection company to the buyer after completing a product inspection, factory audit, or supplier verification. A professional inspection report contains the inspection summary and overall result (Pass, Fail, or Pending), detailed findings organized by category (workmanship, functionality, dimensions, labeling, packaging), photographic evidence (typically 100+ annotated photos), measurement data compared to specifications, AQL sampling results showing defects found versus accept/reject numbers, barcode verification results, and the inspector's observations and recommendations. The report serves as the primary decision-making tool for the buyer: based on its findings, the buyer authorizes shipment, requests rework, negotiates with the supplier, or rejects the lot. High-quality inspection reports also serve as evidence in commercial disputes and insurance claims. Tetra Inspection delivers detailed digital reports within 24 hours of every inspection, accessible through the online client portal.

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What is CPSIA (Consumer Product Safety Improvement Act)?

The Consumer Product Safety Improvement Act (CPSIA) is a United States federal law enacted in 2008 that establishes mandatory safety standards for consumer products, with particular emphasis on children's products. CPSIA is administered and enforced by the U.S. Consumer Product Safety Commission (CPSC). Key requirements include lead content limits (100 ppm total lead in children's products), phthalate restrictions (eight specific phthalates are permanently banned in children's toys and child care articles at concentrations above 0.1%), mandatory third-party testing by CPSC-accepted laboratories, General Certificates of Conformity (GCC) for general-use products, Children's Product Certificates (CPC) for children's products, permanent tracking labels on children's products, and registration cards for durable infant or toddler products. During product inspections, CPSIA compliance is verified by reviewing test reports from accredited labs and confirming that products carry required markings and certifications.

What is CE Marking?

CE marking (an abbreviation of "Conformité Européenne") is a mandatory conformity marking for products sold within the European Economic Area (EEA). The CE mark indicates that a product has been assessed by the manufacturer and found to meet EU safety, health, and environmental protection requirements set out in applicable EU directives and regulations. CE marking applies to a wide range of product categories including electrical equipment (Low Voltage Directive), electromagnetic compatibility (EMC Directive), machinery, toys (Toy Safety Directive), medical devices, personal protective equipment, construction products, and radio equipment. The manufacturer is responsible for conducting the conformity assessment, compiling the technical documentation, issuing the EU Declaration of Conformity, and affixing the CE mark. During quality control inspections, CE compliance is verified by checking that the product bears the CE mark in the correct format, reviewing the Declaration of Conformity, and confirming that required test reports from notified bodies (where applicable) are available.

What is Sample Size?

Sample size in quality control inspection refers to the number of units randomly selected from a production lot for examination during an AQL-based inspection. The sample size is determined by three factors: the total lot size (number of units in the order), the inspection level (General Inspection Level I, II, or III, with Level II being the standard), and the AQL sampling plan tables defined in ISO 2859-1. For example, under General Inspection Level II, a lot of 3,201–10,000 units requires a sample size of 200 units. The sample must be drawn randomly from different cartons and production batches to be statistically representative of the entire lot. A larger sample size provides greater confidence in the inspection result but requires more inspection time. Special inspection levels (S-1 through S-4) use smaller sample sizes and are used when destructive testing is required or when the cost of inspection per unit is high. Understanding sample size selection is fundamental to interpreting inspection results correctly.

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What is Corrective Action Plan (CAP)?

A Corrective Action Plan (CAP) — also called a Corrective and Preventive Action (CAPA) plan — is a structured document that identifies the root cause of a quality or compliance issue found during an inspection or audit and specifies the actions the factory must take to fix the problem and prevent it from recurring. A proper CAP includes the finding description, root cause analysis, immediate containment action, permanent corrective action, responsible person, implementation deadline, and verification method. CAPs are a standard output of factory audits, social compliance audits, and failed product inspections. The buyer or inspection company issues the CAP after reviewing inspection findings, and the factory is expected to respond with their action plan and evidence of implementation. Follow-up inspections or audits verify that corrective actions have been effectively implemented. A well-managed CAP process is the mechanism by which inspection findings drive actual quality improvement in the supply chain.

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What is Barcode Verification?

Barcode verification in quality control inspection is the process of scanning and validating product barcodes (UPC, EAN, FNSKU, QR codes) during a factory inspection to ensure they are readable, correctly encoded, and match the buyer's specifications. Barcode issues are among the most common and costly quality problems in consumer goods: an unreadable barcode can cause shipment rejection at the port, warehouse receiving delays, retail point-of-sale failures, and Amazon FBA listing suppression. During a pre-shipment inspection, the inspector uses a barcode scanner to verify that each barcode type on the product and packaging is scannable, encodes the correct product identifier, matches the packing list, and meets the minimum print quality for reliable scanning. For Amazon FBA sellers, FNSKU barcode verification is critical — Amazon will refuse receipt of products with missing, incorrect, or unscannable FNSKU labels, resulting in disposal fees and listing deactivation.

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What is Packing List Verification?

Packing list verification is the process of checking the actual packed goods in a shipment against the documented packing list to confirm that the correct products, quantities, sizes, colors, and assortments are packed and labeled correctly. During a pre-shipment inspection or container loading check, the inspector counts cartons, selects random cartons to open and verify contents, checks piece counts against the packing list, verifies size and color ratios match the purchase order, and confirms that shipping marks and carton markings are correct. Packing list discrepancies — wrong quantities, mixed sizes, incorrect color ratios, or mismarked cartons — are surprisingly common in overseas manufacturing and can cause significant problems at the destination: inventory errors, customer complaints, and costly returns. Systematic packing list verification during inspection catches these issues before the container is sealed, when corrections are still straightforward.

What is SA 8000?

SA 8000 (Social Accountability 8000) is an international certification standard for social compliance developed by Social Accountability International (SAI). SA 8000 is based on the principles of international human rights norms as described in International Labour Organization (ILO) conventions, the United Nations Convention on the Rights of the Child, and the Universal Declaration of Human Rights. The standard covers nine core areas: child labor, forced or compulsory labor, health and safety, freedom of association and right to collective bargaining, discrimination, disciplinary practices, working hours, remuneration, and management systems. SA 8000 certification requires a third-party audit by an accredited certification body and is valid for three years, subject to surveillance audits. Factories holding SA 8000 certification demonstrate a verified commitment to fair labor practices and safe working conditions, providing buyers with confidence that their supply chain meets international ethical standards.

What is BSCI (Business Social Compliance Initiative)?

BSCI (Business Social Compliance Initiative), now managed by amfori, is a leading supply chain management system that helps companies drive social compliance and improvements within their global supply chains. The amfori BSCI Code of Conduct is based on international labor standards including ILO conventions and the United Nations Guiding Principles on Business and Human Rights. BSCI audits evaluate eleven performance areas: social management system and cascade effect, workers' involvement and protection, freedom of association and collective bargaining, no discrimination, fair remuneration, decent working hours, occupational health and safety, no child labor, special protection for young workers, no precarious employment, no bonded labor, and protection of the environment. Audit results are rated on a scale from A (outstanding) to E (unacceptable). Over 2,700 retailers and brands worldwide participate in the amfori BSCI program, making BSCI audit reports one of the most widely accepted social compliance credentials in international trade.

What is SEDEX (Supplier Ethical Data Exchange)?

SEDEX (Supplier Ethical Data Exchange) is a global membership organization that provides one of the world's largest platforms for sharing responsible sourcing data on supply chains. SEDEX facilitates SMETA (Sedex Members Ethical Trade Audit) audits, which are the most widely used social audit format globally. SMETA audits can be conducted as 2-pillar (covering labor standards and health & safety) or 4-pillar (adding environment and business ethics). SMETA audit reports are uploaded to the SEDEX platform, where they can be shared with multiple buyers, reducing audit fatigue for suppliers who would otherwise need to undergo separate audits for each customer. Over 74,000 organizations across 180 countries are members of SEDEX, including major retailers, brands, and their supply chain partners. For factories, SEDEX membership and a current SMETA audit report demonstrate transparency about working conditions and are increasingly a prerequisite for doing business with large international buyers.

What is Lot Size?

Lot size in quality control inspection refers to the total number of units in the production order or shipment being inspected. The lot size is the foundational variable in AQL-based sampling: it determines the sample size code letter and, combined with the inspection level and AQL value, specifies how many units the inspector must examine. In ISO 2859-1, lot sizes are grouped into ranges (e.g., 501–1,200; 1,201–3,200; 3,201–10,000) with each range corresponding to a specific sample size. When the lot size increases, the sample size also increases, but not proportionally — this is the efficiency of statistical sampling. For inspection purposes, the lot size should include all units of the same product, style, color, and size that were produced under the same conditions. If an order contains multiple styles or significantly different production runs, they should be treated as separate lots for inspection, each with its own sample drawn and evaluated independently.

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What is Quality Management System (QMS)?

A Quality Management System (QMS) is the formalized set of policies, processes, procedures, and records that a manufacturing organization uses to plan, control, and continuously improve the quality of its products and operations. The international standard for QMS is ISO 9001, which provides a framework for organizations to demonstrate consistent ability to provide products that meet customer and regulatory requirements. During a factory audit, the QMS is a primary area of evaluation: auditors review the factory's quality policy, quality objectives, organizational structure, document control, internal audit procedures, management review records, corrective action processes, and continuous improvement initiatives. A well-implemented QMS indicates that the factory has systematic processes for preventing defects rather than relying solely on end-of-line inspection. Factories with ISO 9001 certification have had their QMS independently audited and verified by an accredited certification body.

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What is Amazon FBA Inspection?

An Amazon FBA (Fulfillment by Amazon) inspection is a specialized pre-shipment quality control check designed specifically for products that will be sold through Amazon's marketplace and fulfilled from Amazon's warehouses. In addition to standard product quality checks (workmanship, functionality, dimensions, labeling), an FBA inspection includes Amazon-specific verification requirements: FNSKU barcode readability and accuracy, product packaging compliance with Amazon's prep and labeling requirements, polybag suffocation warning labels where applicable, carton weight and dimension compliance with FBA receiving limits, product condition documentation to prevent "not as described" claims, and product-listing accuracy verification. Amazon FBA inspections are critical because Amazon's receiving process is automated and strict — products that arrive with incorrect barcodes, non-compliant packaging, or quality issues will be rejected, quarantined, or disposed of, resulting in lost inventory, fees, and potential listing suspension.

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What is Inspection Level?

Inspection level is a parameter in the ISO 2859-1 sampling standard that determines the relationship between the lot size and the sample size used during an AQL-based quality control inspection. There are three General Inspection Levels (GIL I, II, and III) and four Special Inspection Levels (S-1, S-2, S-3, S-4). General Inspection Level II (GIL-II) is the default level used for most consumer goods inspections and provides a balanced trade-off between inspection thoroughness and cost. GIL-I uses a smaller sample size (approximately half of GIL-II) and is used when the cost of inspection is high relative to the product value, or when the supplier has a proven quality track record. GIL-III uses a larger sample size (approximately double GIL-II) and is used when higher confidence is required or when the supplier has a history of quality issues. Special inspection levels use significantly smaller samples and are typically used for destructive testing where inspected units cannot be sold.

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