Factory acceptance testing (FAT) is a systematic evaluation of equipment or a system at the supplier’s facility before it ships to the customer. The goal is straightforward: verify that what you ordered actually works the way it should, while it’s still easy and affordable to fix problems. The FDA defines it as “documented evidence that a piece of equipment or system has been adequately tested at the manufacturer’s facility and performed to the end user’s expectations prior to delivery.” In practice, FAT covers everything from checking that hardware matches purchase order specs to running the system at full capacity and confirming software behaves correctly.
Why FAT Matters
The core value of factory acceptance testing comes down to timing. Catching a design flaw, programming error, or specification mismatch while equipment is still on the manufacturer’s floor is dramatically cheaper than discovering it after the system has been shipped, installed, and connected to your utilities. Making changes during the FAT stage avoids the cost of on-site modifications, which can involve tearing out work already completed, ordering new parts with lead times, and halting production schedules.
Beyond cost savings, FAT improves supplier accountability. When both parties agree on acceptance criteria in advance and then test against those criteria together, there’s a clear, documented record of what passed and what didn’t. This reduces disputes later and gives the buyer leverage to ensure problems get resolved before they accept delivery.
What Happens During a FAT
A typical FAT follows a structured sequence, though the specifics vary by industry and equipment type.
Pre-FAT preparation. Before anyone arrives for testing, both the buyer and supplier should agree on a detailed test plan that outlines quality, reliability, and safety requirements. This plan includes functional tests, safety checks (alarms, warnings, emergency shutoffs), and any customer-specific tests beyond the standard scope. Reviewing FAT documents ahead of time reduces testing time significantly. If you know what tests will be run and what the pass/fail criteria are, the actual event moves faster.
Pre-testing by the supplier. Good suppliers run the equipment before the customer shows up. This pre-testing can happen days or weeks in advance. It typically includes a full capacity test or production data report that verifies the unit’s capabilities and flow rates. Running the equipment, even dry running without process materials, is critical. This step catches the most obvious issues so the formal FAT focuses on genuine acceptance rather than troubleshooting basic problems.
Formal FAT execution. The customer’s team (or their representatives) witnesses the testing at the supplier’s facility. This includes visual inspection to confirm the equipment matches purchase order specifications, functional testing of all operating modes, safety system verification, and software checks. For complex systems, the FAT might span two weeks: the first week for initial checkout and identifying issues, the second for integrated functional verification after initial fixes are made.
Punch list and resolution. Any deficiencies found during testing go onto a master punch list, a running document that tracks every issue, its severity, and its resolution status. At the end of the FAT visit, the punch list becomes the vendor’s to-do list. Equipment typically doesn’t ship until all punch list items are completed or formally accepted with a plan for resolution. The FAT is then summarized and given final approval once punch list completion is verified.
Documentation You Should Expect
FAT generates a paper trail that serves you well downstream, particularly during installation and qualification. Key documents include the test protocol itself (with clearly defined procedures and acceptance criteria), calibration certificates for all instruments, material certificates for components, and a final report summarizing results. Calibration records should be attached to the final package, as these prove that the instruments used during testing were themselves accurate.
This documentation pays off quickly. Teams that perform thorough document reviews during FAT often complete the documentation portion of installation qualification in minimal time once equipment arrives on-site, because much of the verification work is already done.
How FAT Differs From SAT
Factory acceptance testing and site acceptance testing (SAT) are complementary steps, not interchangeable ones. FAT happens at the manufacturer’s location. SAT happens at your facility after the equipment is installed. The distinction matters because conditions change between the two.
At the factory, the equipment runs under the supplier’s environmental conditions, using their utilities. Temperature, humidity, compressed air, steam, and other utilities at your site will differ. SAT confirms the equipment still performs correctly under real operating conditions. FAT documentation tends to be very detailed since it covers the full range of functional checks. SAT documentation is simpler, focused on confirming that what passed at the factory still passes after shipping and installation.
When FAT Is Required
Not every piece of equipment needs a formal FAT. Industry guidelines use a risk-based approach to determine when it’s worthwhile. The ISPE’s GAMP 5 guidance, widely followed in pharmaceutical manufacturing, states that FAT is primarily needed for systems involving novel or complex technology. Standard, off-the-shelf software products and configurable systems (GAMP Categories 3 and 4) generally don’t require FAT unless they’re brand new and extremely complex. Custom-built systems (Category 5) may need FAT depending on their type, novelty, and complexity.
The EU GMP Annex 15 on Qualification and Validation, in effect since October 2015, similarly notes that equipment incorporating novel or complex technology may be evaluated at the vendor prior to delivery. The current best practice across life sciences is to apply a risk-based approach: identify the critical functions of the system and then verify those functions during FAT. This keeps testing focused on what actually matters for safety and quality rather than checking every minor feature.
Virtual FAT
Remote or virtual FATs (sometimes called vFATs) became more common when travel restrictions made on-site visits impractical, and many organizations have continued using them for simpler systems. The concept is the same: verify equipment performance against acceptance criteria. The execution, however, requires deliberate planning.
Successful virtual FATs depend on strong communication infrastructure. Each workstream typically runs its own video conference, with continuous connections for breakout conversations and end-of-day briefings. Automation tools that allow remote control of equipment can enable direct testing and setup from a distance. The schedule, roles, and communication plan need to be defined and shared well before testing begins. Teams that skip this planning step consistently struggle, as performing assessments virtually is quite different from being on-site, and unstructured remote FATs tend to drag out or miss issues.
The most important success factor is the working relationship with your vendor. Virtual FAT puts more reliance on the supplier to physically operate equipment, position cameras, and relay observations honestly. Close partnering and clear expectations make or break the process.
Industries That Use FAT
Factory acceptance testing is standard practice across any industry where custom or complex equipment is built to order. Pharmaceutical and biotech companies use it extensively for processing equipment, cleanroom systems, and monitoring platforms. Oil and gas, power generation, water treatment, food and beverage manufacturing, and aerospace all rely on FAT to verify critical systems before shipment. The underlying logic is universal: if the equipment is expensive, difficult to modify once installed, or critical to safety and product quality, testing it at the factory first is worth the investment.