HVAC-Integrated VHP Sterilization System — Technical Solution

A technical solution prepared for a pharmaceutical facility in Saudi Arabia: an HVAC-integrated vaporized hydrogen peroxide (VHP) sterilization system that delivers unattended, dead-zone-free bio-decontamination of two sterile areas through a single FGVHP-1000 unit, integrated directly with the existing HVAC air-handling units.

I. Design Proposal Overview

The Integrated Hydrogen Peroxide Sterilization System by Shanghai Fenggu Pharmaceutical Equipment Co., Ltd. is a professional sterilization solution that seamlessly integrates hydrogen peroxide sterilization equipment with existing HVAC systems. Leveraging the air circulation system of the HVAC system, this system uniformly delivers vaporized hydrogen peroxide (VHP) throughout the spaces requiring sterilization and into the HVAC ductwork, enabling unattended sterilization operations. It ensures thorough sterilization without any dead zones across sterile areas, HVAC supply and exhaust ducts, and the upstream section of HEPA filters. The strong oxidizing power of hydrogen peroxide disrupts the cell membranes, protein and nucleic acid structures of microorganisms, achieving a broad-spectrum sterilization efficacy of 99.9999% (Log6 level) against bacteria, viruses, spores, and other pathogens. The residual hydrogen peroxide after sterilization decomposes into water and oxygen, producing no toxic by-products. This system is particularly suitable for sterile preparation workshops, biopharmaceutical manufacturing facilities, P2 and P3 laboratories, and similar environments.

This equipment consists of a rotary dehumidifier, a high-efficiency filter, a high-pressure fan, CPVC piping, a VHP evaporation unit, and other components; all its primary components are manufactured by internationally renowned brands. Currently, Shanghai Fenggu Pharmaceutical Equipment Co., Ltd. offers three standard models – FGVHP1000 cubic meter, FGVHP2000 cubic meter, and FGVHP3000 cubic meter – for customers to choose from; customized models with larger sterilization volumes can also be provided when required.

According to the user requirements, the disinfection area corresponds to two air conditioning systems – the AHU-S05 and AHU-S06 units – with the sterile room volumes being 362 cubic meters and 418 cubic meters, respectively. During sterilization, the volume of the HVAC return air ducts must also be taken into account; therefore, the actual sterilization volume will be larger. Since the AHU-S05 and AHU-S06 units are located relatively close to each other according to the process layout plan, it is recommended to deploy a single FGVHP-1000 device to perform online VHP sterilization on both spaces. The maximum sterilization capacity of a single FGVHP-1000 unit is 1,000 cubic meters. The detailed schematic diagram of this solution is shown below:

Based on the above parameters and the floor plan, Shanghai Fenggu Pharmaceutical Equipment Co., Ltd. proposes the following design concept:

• Design and install a single FGVHP-1000 generator;
• Two CPVC pipelines are used to connect the VHP generator unit to the supply air ducts of the AHU-S05 and AHU-S06 air conditioning systems, respectively;
• Integration of the VHP generator with the HVAC system for cyclic sterilization of the sterile area;
• Perform area sterilization by controlling the valves on the distribution pipeline;
• The system can perform continuous overnight purification; when switching from AHU-S05 sterilization to AHU-S06 sterilization, no manual intervention is required – the system automatically handles the transition between sterilization zones, and no personnel are permitted in the clean area during the sterilization process.

Sterilization cycle time: approximately 120 minutes; aeration and residual removal time: 1–2 hours. If the exhaust ventilation rate is less than 15 times per hour, the aeration duration should be increased.

II. Sterilization Principle

The FGVHP-1000 Sterilization System leverages the superior sporicidal efficacy of hydrogen peroxide in gaseous form at ambient temperature compared to its liquid form – by generating free hydroxyl radicals that target cellular components — including lipids, proteins, and DNA — to achieve complete sterilization. This system is a specially designed piece of equipment intended for low-temperature sterilization in clean areas.

VHP sterilization is a dry-gas sterilization method; the active VHP does not condense on any surface within the cleanroom, thereby avoiding corrosive damage to most materials.

III. Sterilization Process Description

During operation of the FGVHP-1000, the sterilization cycle consists of four distinct stages:

1. Dehumidification Stage

The humidity in the clean area is maintained below 50% and the temperature is kept above 25°C using the unit’s built-in cold and hot water systems; this process directly determines the effectiveness of the sterilization. During this stage, the VHP generator first preheats the flow in the VHP injection pipeline to serve as a carrier for hydrogen peroxide vapor; during the biodecontamination phase, the concentration of hydrogen peroxide vapor can be maintained below the saturation (dew point) level. Typically, the maximum air flow rate through the FGVHP-1000 biodecontamination system is 300 m³/h; this airflow rate is also influenced by the fan speed of the VHP generator and the limitations imposed by the external piping system.

Note: The time required to reach the target humidity and temperature also depends on the room’s initial humidity, temperature, and volume.

2. Conditioning Phase

The process of continuously increasing VHP concentration; during this process, VHP vapor is continuously injected into the ductwork of the HVAC system. During the conditioning phase, the injection rate of the hydrogen peroxide sterilant is maintained within the range of 50–90 g/min, depending on the volume of the sterilization area required, to achieve the target biodecontamination concentration. The conditioning time is influenced by factors such as the injection rate of the hydrogen peroxide sterilant, the volume of the clean area, and the temperature.

3. Biodecontamination Stage

During this process, by maintaining a low hydrogen peroxide injection rate, the hydrogen peroxide vapor concentration within the room can be kept at a relatively stable level, enabling biodecontamination. During the biodecontamination process, the gas concentration within the biodecontamination zone is uniformly distributed. During the biodecontamination phase, the HVAC cooling and heating units are turned off. Biodecontamination conditions: 25–30°C, 30–50% relative humidity. The biodecontamination zone is controlled by operating the control valve for entering/exit areas.

4. Aeration Phase

Stop the injection of hydrogen peroxide sterilant vapor; continue to supply the VHP generator with a dry air stream to purify the internal piping of the VHP equipment. Simultaneously, activate the disinfection exhaust fan in the HVAC system to operate under a fully fresh-air, fully exhaust mode. This step is intended to reduce the concentration of hydrogen peroxide sterilant vapor within the room; once the hydrogen peroxide gas concentration in the room falls below 1 ppm, terminate the aeration process and resume normal operation of the air conditioning system. When necessary, the FGVHP-1000 can also control the external ventilation system.

IV. VHP Sterilization System Technical Specifications

The Shanghai Fenggu FGVHP-1000 sterilizer is integrated with the client’s HVAC system for the biological decontamination and sterilization of sterile pharmaceutical facilities. The sterilizer is installed in the client’s air conditioning equipment room and is connected via piping to the exhaust air conditioning unit’s pipeline system. The main technical parameters of the sterilization system are listed in the table below:

V. VHP Sterilization System Configuration List

The Shanghai Fenggu VHP Sterilization System consists of a rotary dehumidifier, a main generator unit, a pipeline distribution system, and an automatic control system; the detailed configuration and brand information are shown in the table below:

VI. Overview of the Pipeline Circulation System

VHP pipeline

• Made of CPVC, ensuring the system is leak-proof.
• The pipeline is equipped with insulation measures to prevent the condensation of hydrogen peroxide gas.

Ventilation duct system

• The air conditioning ventilation duct system must be airtight; during construction, the sealing of all duct connections should be carefully inspected, as any leakage of hydrogen peroxide gas could occur.
• Control valves are installed on the main pipeline and branch pipelines to distribute hydrogen peroxide gas.

VII. Scope of Supply

Fenggu Supply Scope

• Design Specification Sheet (DS);
• VHP generator main unit, connection unit for the ventilation duct system, and control system;
• Public Utilities Requirements – Installation Guidelines for Hydrogen Peroxide Distribution Pipelines;
• Sensor for monitoring VHP concentration on HVAC return air ducts;
• Installation supervision and guidance;
• Development of sterilization processes; assisting clients in preparing validation documentation; and assisting clients with the validation of chemical and biological indicators;
• Remote host computer.

Customer Scope of Work

• VHP module installation and positioning;
• On-site utility connections, including the main power distribution circuit and reserved interfaces for compressed air pipelines near the equipment;
• Verification implementation;
• Operators receive training.

VIII. File System

Shanghai Fenggu employs a team of technical personnel with extensive pharmaceutical industry experience, capable of assisting clients in establishing documentation systems that comply with cGMP requirements; the primary documentation to be submitted for the VHP sterilization system is outlined in the table below:

IX. Important Notes

1. Shanghai Fenggu recommends providing the equipment with a dedicated grounding circuit.
2. The device should not be used in areas where it is not compatible with VHP.
3. The biodecontamination system must be installed on a rigid horizontal surface.
4. A simulated VHP sterilization challenge test must be conducted on the color-coated steel sheets and air ducts within the cleanroom area.
5. The FGVHP-1000 biodecontamination system must be cleaned regularly.
6. Weight: approximately 380 kg.
7. The user is obliged to arrange cyclic verification.

X. Annex: Integrated vs Mobile VHP Sterilization Systems

The integrated VHP sterilization system offers the following advantages compared to mobile hydrogen peroxide sterilization systems:

Taking a 1000 m³ sterile Class B zone as an example – assuming this zone comprises 12 rooms – at least three mobile VHP sterilizers would be required to complete the sterilization process for the entire area; however, using an integrated hydrogen peroxide sterilization system would require only a single FGVHP1000 unit to accomplish the sterilization. During operation, unlike with mobile VHP sterilizers, the FGVHP1000 does not need to push each individual unit into the sterile zone before initiating sterilization; instead, VHP is delivered via pre-installed piping systems. The FGVHP1000’s remote host computer is installed in the HVAC control room, enabling the sterilization process to be carried out directly from this room. Through integration with the HVAC system’s programming, the sterilization sequence – including sterilization preparation, VHP circulation, and VHP exhaust – can be executed fully automatically; upon completion of sterilization, the HVAC system will automatically revert to production mode. After sterilization is finished, there is no need for the operator to don sterile clothing and enter the Class B zone to remove the mobile VHP sterilization unit.

If multiple mobile VHP sterilization units are required, each device must be inspected for its operational status and topped up with hydrogen peroxide solution before powering on – a process that involves significant labor costs as it constitutes a manual sterilization method. When using mobile VHP sterilization units, the concentration of hydrogen peroxide near these devices can become extremely high during the sterilization process, which may readily corrode the surrounding color-coated steel sheets. However, if an integrated air-conditioning-based hydrogen peroxide sterilization system is employed, this issue is avoided: the VHP injection is delivered through heating and ventilation ducts, and each room is equipped with hydrogen peroxide steam distribution outlets, thereby eliminating the risk of localized excessive concentration.

The mobile VHP sterilizer operates on a manual sterilization basis; however, variations in the placement of each unit during individual sterilization cycles can affect the sterilization outcome – an issue that is inherently difficult to avoid in manual operation. Practical experience has shown that the sterilization efficacy of mobile VHP sterilization systems exhibits very poor repeatability. In contrast, the integrated hydrogen peroxide sterilization system, which delivers the solution to each chamber via a centralized heating and ventilation duct, avoids this problem. During the sterilization process with the integrated hydrogen peroxide system, the fan speed of the HVAC supply fan, the supply air volume, and the opening/closing angle of the supply/extract air volume valves are all maintained at fixed values, resulting in excellent repeatability of the sterilization efficacy.

The integrated hydrogen peroxide sterilization system is highly scalable; for example, when eight sterile areas require sterilization, a single integrated hydrogen peroxide sterilization system can be deployed to sterilize each area by distributing the solution through eight separate pipelines and valves. All sterile areas can be automatically sterilized in sequence using a preconfigured program, or the system can be configured in advance to support future VHP sterilization operations in newly constructed workshops. As a result, such workshops will not need to purchase additional VHP sterilization equipment – they simply need to install new sterilization pipelines.