Leak detection of high-efficiency filters (HEPA/ULPA) is a critical part of cleanroom validation.
With the implementation of GMP standards, especially in pharmaceutical industries, HEPA filter leak testing has become a mandatory inspection requirement.
Today, industries such as pharmaceuticals, bệnh viện, electronics, food, and cosmetics all require reliable HEPA filter integrity testing to ensure cleanroom performance.
Below are five common HEPA filter leak detection methods used in practice.
1. Sodium Flame Method
The sodium flame method uses sodium chloride (NaCl) aerosol as the test challenge.
The aerosol is generated by atomizing a salt solution using compressed air. After drying, fine salt particles enter the air duct. Air samples are taken upstream and downstream of the filter and introduced into a hydrogen flame.
The presence of sodium causes the flame to change color and brightness, which is used to estimate particle concentration and filter efficiency.
Hạn chế:
- Low sensitivity
- Not suitable for HEPA/ULPA filters
- Rarely used in modern testing systems
2. Oil Mist Method
The oil mist method uses oil aerosols (typically paraffin oil) with particle sizes around 0.3–0.5 μm.
Filter performance is evaluated by comparing the turbidity (opacity) of air upstream and downstream of the filter.
Hạn chế:
- May contaminate or damage filters
- Results are not directly readable
- Time-consuming
3. DOP Method (Traditional Standard Method)
The DOP method has historically been one of the most widely used methods for HEPA filter testing.
It uses dioctyl phthalate (DOP) aerosol particles with a size of approximately 0.3 mm. The aerosol is generated by heating DOP liquid, forming vapor that condenses into fine droplets.
Filter efficiency is determined by measuring aerosol concentration before and after the filter.
Notes:
- Now often replaced by safer alternatives (ví dụ., PAO)
- Still referenced in older standards and practices
4. Fluorescence Method
This method uses sodium fluorescein particles generated by a sprayer.
Air samples are collected before and after the filter, and the particles are dissolved in water. The fluorescence intensity of the solution is measured to determine particle concentration and filtration efficiency.
Hạn chế:
- Complex process
- Requires laboratory analysis
- Not suitable for real-time leak detection
5. Particle Counting Method (Scanning Method)
The particle counting method is currently the most widely used and internationally accepted method for HEPA filter leak detection.
It complies with standards such as:
- TRONG 1822
- ISO 29463
Nó hoạt động như thế nào
- Bình xịt (ví dụ., DEHS or PAO) is introduced upstream
- A particle counter measures particle concentration
- The entire filter surface is scanned point by point
- Local leaks are detected based on particle concentration differences
Thuận lợi
- High sensitivity
- Real-time detection
- Accurate leak localization
- Suitable for HEPA and ULPA filters
Giải pháp được đề xuất: Automatic HEPA Filter Scanning Test Bench
For modern HEPA filter manufacturers and cleanroom applications, cái particle counting scanning method is the most reliable solution.
Equipment such as the Bàn kiểm tra rò rỉ bộ lọc HEPA SC-L8023 is designed for:
- Automatic scanning of the full filter surface
- Phát hiện rò rỉ có độ nhạy cao
- Tạo khí dung ổn định
- Compliance with EN 1822 và ISO 29463
The system uses a high-precision particle counter and scanning mechanism to ensure consistent and repeatable testing results, making it ideal for production lines and quality control laboratories.
Phần kết luận
Among the five methods, traditional techniques such as sodium flame, sương dầu, and fluorescence methods are gradually being replaced.
Today, cái particle counting scanning method has become the industry standard due to its accuracy, hiệu quả, and compliance with international standards.
For manufacturers aiming to meet strict quality requirements, investing in an automatic HEPA filter leak test system is essential.
