Medical device immersion testing evaluates how finished devices, subassemblies, and materials perform when fully or partially submerged in water, cleaning agents, disinfectants, or simulated body fluids. It verifies ingress protection ratings (IPX7/IPX8), post-immersion electrical safety, material compatibility, and extractables behavior in accordance with IEC 60529, IEC 60601-1, ISO 10993, and ASTM standards. This guide explains the sample types, test items, methods, and applications that make up a complete immersion testing program for medical devices.
Technical Overview
Medical device immersion testing is a laboratory verification process in which a finished device, a subassembly, or a material specimen is submerged in a controlled liquid—water, detergent, disinfectant, or simulated body fluid—at a defined depth, temperature, and duration. The objective is to demonstrate that the product resists harmful liquid ingress, remains electrically safe, and retains its material and functional integrity after exposure to fluids encountered during cleaning, disinfection, sterilization, storage, transport, or clinical use.
The governing framework draws on several complementary standards: IEC 60529 (adopted in China as GB/T 4208 and in Japan as JIS C 0920) defines the IP code, including the IPX7 and IPX8 immersion ratings; IEC 60601-1 (and national adoptions such as EN 60601-1, UL 60601-1, and GB 9706.1) requires medical electrical equipment to substantiate any declared ingress protection claim; ISO 175, ASTM D543, and ASTM D471 cover the chemical resistance of plastics and elastomers; ASTM D570 addresses water absorption; and the ISO 10993 series governs extraction and chemical characterization for biocompatibility. Because a single product may face multiple fluid-contact scenarios across its life cycle, accredited third-party laboratories typically structure immersion testing as a matrix covering the assembled device, material coupons, and simulated-use soak exposures aligned with the manufacturer's processing instructions under ISO 17664-1.
Testing Samples
Finished Electrical and Electronic Devices
Patient monitors, infusion pumps, wearable sensors, digital thermometers, hearing devices, powered surgical handpieces, and mobility aids are tested as fully assembled, production-representative units to verify their declared IPX ratings and post-immersion electrical safety. A minimum of three units is customary so that sealing consistency across the manufacturing process can be assessed.
Enclosures, Seals, and Connectors
Housings, gaskets, O-rings, cable glands, membrane keypads, and interconnect assemblies are submerged individually or as built-up subassemblies to confirm seal effectiveness, joint integrity, and the behavior of potting compounds and adhesives under prolonged wetting.
Polymeric and Elastomeric Materials
Coupon-level specimens—plaques, strips, and tensile dumbbells—of engineering plastics, silicones, thermoplastic elastomers, coatings, and adhesives are immersed in standardized reagents to quantify swelling, mass uptake, and mechanical property retention.
Reprocessable Surgical Instruments
Instruments intended for repeated immersion in enzymatic detergents and high-level disinfectants are tested after a worst-case number of simulated reprocessing cycles to confirm cleaning efficacy, residue removal, and material compatibility.
Implants and Long-Term Fluid-Contact Devices
Catheters, extracorporeal tubing sets, stents, and orthopedic or dental implants are soaked in saline or simulated body fluid at physiological temperature to evaluate degradation, corrosion, and leachables over the intended contact duration.
Sterile Barrier Packaging
As part of packaging validation under ISO 11607-1, sealed pouches and trays may undergo water-bath immersion challenges followed by seal strength and leak testing to confirm that fluid exposure during transport or handling does not compromise sterility.
Testing Items
Depending on product type and risk profile, a typical immersion test program includes the following items:
- Water ingress verification against IPX1 through IPX8, most commonly IPX7 and IPX8 immersion ratings
- Post-immersion electrical safety: dielectric strength, insulation resistance, earth leakage, and touch/leakage current per IEC 60601-1
- Functional and operational checks after immersion and drying
- Visual inspection and microscopy for corrosion, swelling, cracking, blistering, delamination, and color change
- Mass change, dimensional change, and water absorption per ASTM D570
- Mechanical property retention: tensile strength and elongation (ASTM D638, ISO 37), hardness (ASTM D2240), and flexural or impact performance
- Seal and joint integrity after immersion, using dye penetration or bubble emission techniques
- Extractables and leachables profiling per ISO 10993-12 and ISO 10993-18
- Cytotoxicity screening of immersion extracts per ISO 10993-5
- Electrochemical corrosion behavior of implant metals in simulated body fluid per ASTM F2129
- Cleaning efficacy and residual soil analysis after immersion washing cycles, following the concepts of ISO 15883-5
Testing Methods
Ingress Protection Immersion (IPX7 / IPX8)
Per IEC 60529 and its national equivalents, the IPX7 test submerges the enclosure so that its lowest point sits at least 1 m below the water surface (or its highest point at least 0.15 m below the surface for tall enclosures) for 30 minutes. The IPX8 test applies continuous immersion at a depth and duration agreed between manufacturer and laboratory. After removal and draining, the specimen is opened and inspected: harmful water ingress affecting insulation or live parts constitutes failure, and powered devices are subsequently subjected to dielectric and leakage current testing.
Chemical Resistance Immersion
Following ASTM D543, ASTM D471, ISO 175, or GB/T 11547, material specimens are immersed in reference reagents—water, saline, alcohols, sodium hypochlorite, peracetic acid, glutaraldehyde, quaternary ammonium detergents, and lubricating oils—for periods such as 1, 3, or 7 days at 23 °C, with extended or elevated-temperature exposures for long-contact claims. Measured properties are compared with unexposed controls, and results are reported as percentage change with visual rating.
Water Absorption Testing
ASTM D570 specifies conditioning specimens to constant weight, then immersing them in water at 23 °C for 24 hours (with optional boiling-water and long-term immersion protocols). The percentage mass gain indicates the moisture sensitivity that drives swelling, dimensional instability, and degradation of electrical properties.
Extraction for Chemical Characterization
Under ISO 10993-12, device portions are immersed at standardized ratios—commonly 3 or 6 cm² of surface area per milliliter of extractant, or 0.1–0.2 g/mL for irregular solids—in polar and nonpolar media such as water, saline, ethanol/water, and hexane. Extraction conditions such as 37 °C for 72 hours, 50 °C for 72 hours, 70 °C for 24 hours, or 121 °C for 1 hour are selected according to the device's body-contact conditions. The resulting extracts are analyzed by GC-MS, LC-MS, HPLC, and ICP-MS per ISO 10993-18, with toxicological risk assessment conducted per ISO 10993-17.
Simulated-Use and Reprocessing Immersion
Devices are contaminated with defined test soil, then subjected to repeated immersion in detergent and disinfectant solutions at the concentrations, temperatures, and contact times stated in the manufacturer's instructions (consistent with ISO 17664-1). After a worst-case number of cycles, cleanliness is verified through residual protein, hemoglobin, and total organic carbon assays, and the device is reassessed for material and functional integrity.
Simulated Body Fluid Immersion for Implantables
Implants and long-term fluid-contact devices are soaked in phosphate-buffered saline at 37 °C for the intended duration of body contact, with periodic retesting of mechanical properties. Metallic devices may additionally undergo cyclic potentiodynamic polarization per ASTM F2129, while degradation products are characterized per ISO 10993-15 for metals, ISO 10993-13 for polymers, and ISO 10993-14 for ceramics.
Applications
Immersion testing data supports medical device development and market access in several key ways:
- Regulatory submissions and conformity demonstration for EU MDR CE marking, US FDA 510(k) and PMA reviews, China NMPA registration under GB/T 4208 and GB 9706.1, and Japanese approval under JIS C 0920
- Design verification and validation of waterproof ratings and cleaning claims prior to labeling
- Material selection, formulation comparison, and supplier qualification during development
- Validation of reprocessing instructions for reusable instruments
- Support for shelf-life and accelerated aging studies involving liquid exposure
- Bat-ch-to-batch quality control and incoming material inspection for fluid-contact components
- Failure analysis and complaint investigation following water damage or chemical exposure events
FAQ
What is the difference between IPX7 and IPX8 testing?
IPX7 is a fixed-condition test: 30 minutes of immersion with the device approximately 1 m under water. IPX8 verifies continuous immersion at a depth and duration specified by the manufacturer, which must exceed the IPX7 severity to be meaningful. Both are defined in IEC 60529.
Must the device be powered during the immersion test?
Not necessarily. Devices that are only rated for protection when unpowered or de-energized are tested in the off state, whereas devices claimed to operate in or immediately after immersion are energized or functionally exercised as part of the evaluation.
Which liquids are used in immersion testing?
Deionized or tap water is used for ingress protection tests; detergent, disinfectant, and chemical reagent solutions are used for compatibility studies; and saline or simulated body fluids are used for implant-related soaks and extraction testing.
How are results judged?
Acceptance criteria are defined in advance based on the declared rating, applicable standards, and intended use. Typical criteria include no harmful ingress, pass results on dielectric and leakage tests, retention of at least a defined percentage of mechanical properties, and no visually evident degradation such as cracking or corrosion.
How long does an immersion testing program take?
Simple IPX7 verification can be completed within a few days including inspection and electrical retesting. Chemical resistance and extraction programs involving multi-day exposures, analytical characterization, and repeated reprocessing cycles may require several weeks to complete.
Is immersion testing mandatory for all medical devices?
It is required whenever the manufacturer declares a liquid-related claim—such as an IPX rating, immersion cleanability, or fluid contact—or when the intended use and risk analysis identify fluid exposure as a foreseeable hazard. Accredited third-party laboratories can help scope a program appropriate to the device classification.