Particle Counting Services

Healthcare HVAC Particle Counting: 

What it is:

Healthcare HVAC (Heating, Ventilation, and Air Conditioning) particle counting is a process used to measure and monitor the number and size of airborne particles within healthcare environments, such as hospitals, cleanrooms, operating theaters, laboratories, and pharmaceutical manufacturing areas. It is a key aspect of air quality control and infection prevention, ensuring that ventilation systems maintain clean air in sensitive areas.

Why it matters:

In healthcare settings, airborne particles can include dust, skin flakes, microorganisms (like bacteria and viruses), and other contaminants that can compromise sterile environments and pose a risk to patients, especially during surgeries or in immunocompromised care units. HVAC systems must maintain specific cleanliness levels to comply with standards (e.g., ISO 14644, USP <797>, or ASHRAE guidelines).

What Particle Counting Involves:

Use of Particle Counters:

Instruments called laser particle counters or optical particle counters (OPCs) are used to detect and count airborne particles.

They measure particles typically in the size range of 0.3 to 10 microns, often focusing on key sizes like 0.3 µm, 0.5 µm, and 5.0 µm (important for cleanroom classifications).

Sampling Locations:

• Air samples are taken at critical points: near HEPA filters, air returns, surgical tables, laminar flow cabinets, and other high-risk areas
• Both supply air (what’s coming out of the HVAC) and ambient air (what's in the room) are monitored.
• Frequency and Protocols:

Particle counting is done:

• During commissioning of new or upgraded HVAC systems.
• Periodically (e.g., quarterly or semiannually) as part of routine monitoring.
• In real-time, using continuous monitoring systems in high-risk areas.
• Results are compared against cleanroom classifications (ISO 7, ISO 8, etc.) or facility-specific cleanliness requirements.

Data Analysis and Reporting:

• Results help determine the effectiveness of filtration systems, air changes per hour (ACH), and air pressure differentials.
• Alerts can be set for when particle levels exceed safe thresholds, prompting maintenance or corrective action.

Regulatory Compliance:

• Compliance with standards such as:
• ISO 14644-1 for cleanrooms.
• USP <797> and USP <800> for pharmaceutical compounding.
• ASHRAE 170 for ventilation in healthcare facilities.
• FDA and CDC guidelines in clinical and surgical environments.

Summary:

Particle counting in healthcare HVAC systems is a vital procedure for maintaining sterile and safe air quality. It involves using sophisticated equipment to measure airborne particulate matter, ensuring compliance with cleanliness standards, and ultimately protecting patient health. The process supports infection control, product integrity (in pharmaceutical settings), and the overall safety of clinical environments.

What Is European Vacuum Testing (EVT)?

European Vacuum Testing (EVT) is a standardised method for evaluating the cleanliness of ventilation ductwork systems. It is a quantitative inspection technique involving vacuum sampling of settled dust from duct surfaces, followed by laboratory analysis to assess compliance with hygiene standards.

This method is recognised and recommended in:

• BS EN 15780 – Cleanliness of Ventilation Systems
• TR19 (BESA) – Guidance on Cleanliness and Maintenance of HVAC Systems

Purpose of EVT

Primary goal: To quantify the amount of dust and particulate residue present inside ventilation ducts.

Applicable to: All duct shapes — circular, flat-oval, and rectangular.

Use cases:

• Commissioning of new ductwork systems.
• Verification of post-cleaning effectiveness.
• Ongoing maintenance compliance checks.

What Is Active Air Sampling?

Active air sampling is a quantitative microbiological method that draws a known volume of air through a collection medium (e.g. agar plate) using a mechanical air sampler, to detect and measure airborne viable microorganisms such as bacteria and fungi.

It is distinct from passive air sampling (e.g. settle plates), which relies on gravity-based particle deposition.

Purpose of Active Air Sampling

    •    Detect airborne microbial contamination

    •    Quantify colony-forming units (CFUs) per cubic meter of air (CFU/m³)

    •    Monitor compliance with regulatory standards in:

    •    Pharmaceutical manufacturing (e.g. EU GMP Annex 1)

    •    Healthcare clean zones (e.g. operating theatres)

    •    Biotech, aerospace, and food processing

How It Works

1. Air Sampler Device draws a precise volume of air, typically 100–1000 liters, through a collection medium.

Common types:

    •    Impaction samplers (e.g. slit-to-agar or sieve samplers)

    •    Centrifugal samplers

    •    Liquid impingers (e.g. AGI-30)

2. Collection Medium

    •    Agar plates (usually 90 mm Petri dishes):

    •    TSA (Tryptic Soy Agar) – for bacteria

    •    SDA (Sabouraud Dextrose Agar) – for fungi

    •    R2A or blood agar – for specialized organisms

3. Sampling Process

The sampler is placed in the environmental zone to be tested (e.g. ISO 5–8 cleanrooms).

A known volume of air is sampled (e.g. 1,000 L).

Airborne particles impact on agar surface, depositing viable microbes.

Plates are then incubated at specific temperatures:

    •    30–35°C for bacteria (48–72 hours)

    •    20–25°C for fungi (up to 5–7 days)

4. CFU Counting and Reporting

After incubation, visible colonies are counted.

Results are expressed as:

                    Total CFUs counted

 CFU/m3 = ______________________

                   Sampled volume (in m3)

What Is DOP Testing?

DOP testing is a qualitative or quantitative leak/integrity test performed on High-Efficiency Particulate Air (HEPA) or Ultra-Low Penetration Air (ULPA) filters to verify they:

Meet the required filtration efficiency (typically ≥99.97% for 0.3 µm particles).

Do not leak under operational conditions.

DOP originally stood for Dioctyl Phthalate, the first challenge aerosol used. Today, safer substitutes like PAO (polyalphaolefin) are commonly used, but the term “DOP test” is still widely used generically.

Purpose and Applications

To confirm filter integrity after manufacturing, transport, installation, or service.

Required by standards and regulations for controlled environments:

• ISO 14644-3
• EN 1822
• IES-RP-CC-001
• FDA GMPs (for pharma/biotech)
• BS EN 12469 (for microbiological safety cabinets)

Industries:

• Pharmaceutical cleanrooms
• Semiconductor facilities
• Hospitals and surgical suites
• Biosafety laboratories (BSL-2, BSL-3, BSL-4)
• Food processing and microelectronics

Annual Verification Overview (HTM 03-01 Part B)

Annual verifications are statutory inspections and performance tests carried out to confirm that healthcare ventilation systems:

    •    Deliver sufficient air changes per hour (ACH)

    •    Maintain correct pressure differentials between adjacent rooms

    •    Provide effective filtration (HEPA where required)

    •    Ensure cleanliness and airflow directionality

    •    Support environmental monitoring (e.g. temperature, humidity, and airborne bioburden)

These tests must be conducted by a Competent Person (Ventilation) or Authorised Person (Ventilation), as designated under HTM 03-01.

Components of Annual Verification

1. Airflow and Air Change Rates (ACH)

    •    Measured using balometers, anemometers, or flow hoods.

    •    Ensures sufficient fresh or filtered air is introduced.

    •    Typical requirements:

      ◦    Operating theatres: 20–25 ACH

      ◦    Isolation rooms: ≥10 ACH

      ◦    Clean rooms: Varies by classification (e.g. ISO 7 or ISO 8)

2. Pressure Differentials

    •    Critical for infection containment or exclusion:

      ◦    Positive pressure in clean zones (e.g. theatres) to prevent ingress.

      ◦    Negative pressure in isolation rooms to contain pathogens.

    •    Verified using manometers or differential pressure monitors.

    •    Typical differential: ≥10 Pa between zones.

3. Filtration Testing

    •    Visual inspection and performance verification of:

    ◦    HEPA filters (integrity tested via DOP/PAO testing)

    ◦    Pre-filters and secondary filters

    •    Ensures compliance with BS EN 1822 for HEPA classification and efficiency.

4. Active Air Sampling

    •    Conducted to assess microbiological air quality.

    •    Viable airborne microorganisms are sampled (in CFU/m³) via:

      ◦    Impaction samplers (e.g., SAS, MAS-100)

      ◦    Followed by agar incubation and colony counting.

    •    Required in clean-critical areas (e.g., operating theatres, sterile prep rooms).

5. Smoke Visualisation Testing

    •    Used to confirm airflow directionality and clean-to-dirty airflow paths.

    •    Involves releasing visible smoke (e.g., glycerol-based) and observing flow patterns.

6. System Functionality & Alarm Testing

    •    Ensures sensors and control systems (e.g., alarms for flow/pressure faults) operate correctly.

7. Cleanliness Verification

    •    Duct inspections and particulate sampling.

    •    Sometimes includes vacuum testing (EVT) or swab sampling.

Reporting and Documentation

The verification report should include:

    •    Summary of all tests performed

    •    Pass/fail status for each parameter

    •    Deviations from HTM 03-01 limits

    •    Remedial actions required (if any)

    •    Calibration records of measuring devices

    •    Signature of Competent/Authorised Person

    •    Date of next scheduled verification