By Laurent Berliet
In the pharmaceutical industry, where product sterility is a non-negotiable regulatory requirement, mastering steam sterilization processes is essential. The Bowie-Dick test and other hollow Process Challenge Devices (PCDs), such as the Helix test, are often perceived as simple daily checks. Yet, they play a critical role in ensuring the safety and sterility of pharmaceutical products.
Designed to verify the effectiveness of air removal and uniform steam penetration into porous loads and hollow devices, these tests are key elements in monitoring pre-vacuum autoclaves. They act as preventive barriers against invisible failures in the sterilization cycle. Their correct and documented execution is essential to meet strict regulatory requirements such as ISO 17665 and Annex 1 of the European GMP, which state:
ANNEX 1 |
Clause 8.61 There should be adequate assurance of air removal prior to and during sterilisation when the sterilisation process includes air purging (e.g. porous autoclave loads, lyophilizer chambers). For autoclaves, this should include an air removal test cycle (normally performed on a daily basis) or the use of an air detector system. Loads to be sterilised should be designed to support effective air removal and be free draining to prevent the build-up of condensate. |
ISO 17665:2024 |
A.10 Routine monitoring and control A.10.4 Persons responsible for sterilization should ensure that before the sterilizer is used for production, they have evidence to show that : |
ISO 17665:2024 |
A.12.3 Daily air removal and Steam penetration test A.12.3.1 The test cycle for carrying out the daily steam penetration test (e.g. the Bowie and Dick Test) should use the same operating cycle as that used for sterile product production. The steam penetration test is designed to assess the ability of the production process to effect air removal and rapid and even steam penetration into the PCD. If using a test cycle that is modified from the operating cycle, the air removal stage is identical rather than being a specially designed test cycle. If such a test cycle is used, it is only acceptable to adjust the holding time of the test cycle in order to match the specified exposure time and temperature indicated in the instructions for use accompanying the challenge device (e.g. some commercially produced test devices specify a holding time of 3,5 min), or reduce the drying time of the test cycle. Reference can be made to ISO 11140-4 AND ISO 11140-6 which describes the performance requirements for steam penetration test devices used for carrying out a daily steam penetration test in an empty chamber. |
ISO 17665:2024 |
Table H1: Routine monitoring and control of sterilizing equipment in an industrial setting Steam penetration test: Can be performed for every cycle and/or an alternative equivalent quality control method can be used that includes use of Bowie and Dick /PCD tests daily to establish acceptable steam penetration Periodic steam penetration test (Bowie and Dick/hollow load PCD) can be performed daily or Can be unnecessary where cycle steam penetration test are performed |
Developed in the 1960s, the Bowie-Dick test assesses the autoclave’s ability to remove air and ensure uniform steam penetration into challenging loads such as porous materials, blisters, and hollow devices. Though originally designed for hospital use, it has become a standard in industrial sterilization, particularly under GMP guidelines.
This test simulates a porous load (e.g., linens, filters, packaging) and can detect:
Typically, the classic test pack consists of multiple layers of fabric or paper and a chemical indicator sensitive to temperature and steam. Proper air removal allows saturated steam to reach the reactive ink, resulting in a uniform color change.
The Helix test is another PCD system designed to evaluate vacuum quality and steam penetration, particularly in hollow devices such as tubing and hoses—common in pharmaceutical environments. Compliant with ISO 11140-6, the Helix test uses a coiled tube leading to a cavity containing a chemical indicator. A successful test requires saturated steam to reach the indicator, confirming effective air removal.
Following above publication of Annex 1 (2022) and the reinforcement of ISO 17665 requirements, daily Bowie-Dick testing using classic packs compliant with ISO 11140-4 has become a widespread practice in the pharmaceutical industry. While this approach ensures regulatory compliance, it raises growing concerns regarding its environmental footprint.
Each traditional Bowie-Dick pack weighs approximately 120 grams and is designed for single use only. When used daily, this results in a substantial accumulation of non-recyclable waste. Over the course of a year, a single autoclave can generate over 40 kilograms of disposable material, which must be collected, transported, and processed—often through incineration or landfill.
Beyond the waste itself, the transportation of bulky cartons containing these packs adds another layer of environmental impact. The logistics involved in distributing thousands of units across production sites contribute to CO2 emissions, packaging waste, and increased operational costs.
In an industry increasingly committed to sustainable practices, the ecological burden of traditional Bowie-Dick testing is no longer negligible. There is a clear need for alternative solutions that maintain compliance while significantly reducing waste and environmental impact.
In a context where operational efficiency must align with sustainability goals, the industry is increasingly seeking smarter, greener alternatives.
In response to the growing ecological concerns associated with traditional Bowie-Dick testing, Mesa Labs has taken a proactive approach. In our ongoing commitment to environmental sustainability, Mesa Labs is dedicated to reducing the environmental impact of its products by evaluating the possibility to introduce a reusable Process Challenge Device (PCD) designed to comply simultaneously with ISO 11140-4 (Bowie-Dick test) and ISO 11140-6 (for hollow and porous devices).
This solution—the Bowie-Dick Simulation Test®—offers a hybrid approach that combines the reliability of chemical indicators with the efficiency of reusable components. By significantly reducing the volume of waste generated compared to traditional single-use packs, it directly addresses the environmental challenges faced by the industry.
Not only does it maintain full regulatory compliance, but it also supports pharmaceutical companies in achieving their sustainability objectives, lowering both operational costs and carbon footprint associated with transport and disposal of disposable test materials.
ISO 11140-4 Sterilization of health care products — Chemical indicators Part 4: Class 2 indicators as an alternative to the Bowie and Dick-type test for detection of steam penetration
ISO 11140-5 Sterilization of health care products — Chemical indicators Part 5: Class 2 indicators for Bowie and Dick-type air removal tests
ISO 11140-6 Sterilization of health care products — Chemical indicators Part 6: Type 2 indicators and process challenge devices for use in performance testing of small steam sterilizers
ISO 17665:2024 Sterilization of health care products — Moist heat — Requirements for the development, validation and routine control of a sterilization process for medical devices
European Commission. (2022). The rules governing medicinal products in the European Union, Volume 4: EU guidelines for good manufacturing practice for medicinal products for human and veterinary use. Annex 1: Manufacture of sterile medicinal products
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