Lecture Notes: Determination of Volatile Organic Compounds (VOCs)

Date: 28/11/2012

Presenter: Mr. Tim Wong, Accreditation Officer, Hong Kong Accreditation Service

Contents

• Definitions
• Sources
• Hazards
• Sampling and Analytical Methods
• Accreditation

Definitions

Selected Definitions from Hong Kong and Overseas

• Hong Kong Air Pollution Control (VOCs) Regulation (CAP 311W):

  • VOC: Any volatile compound of carbon excluding methane, carbon monoxide, carbon dioxide, carbonic acid, metallic carbides, metallic carbonates, ammonium carbonate, and exempt compounds.

• World Health Organization (1989):

  • Very volatile organic compound (VVOC) < 0 up to 50°C
  • Volatile organic compound (VOC) 50-100 up to 240-260°C
  • Semivolatile organic compound (SVOC) 240-260 up to 380-400°C

• United Nations Economic Commission for Europe (UN ECE protocol, Nov. 1991):

  • Organic compounds of anthropogenic nature, excluding methane, capable of producing photochemical oxidants by reacting with nitrogen oxides in sunlight.

• US Environmental Protection Agency (US EPA):

  • Similar definition to Hong Kong's regulation, relating to ozone formation.

• European Union (2001/81/EC National Ceiling Directive):

  • VOCs from human activity other than methane, capable of producing photochemical oxidants with nitrogen oxides in sunlight, related to ozone formation.

Sources

Potential Sources of VOC Emissions

• Ambient mobile and stationary sources (e.g., benzene from automotive exhaust and vapor release from gasoline stations).
• Off-gassing of chemicals from furniture (e.g., formaldehyde from particleboard desks).
• Construction, demolition, and building renovation activities (e.g., painting walls).
• Personal hygiene products (e.g., perfumes and hairsprays).
• Pesticides and insecticides.
• Commercial activities (e.g., automotive painting and dry cleaning exhausts).

Hazards

Health Effects of VOCs

• Carcinogenic Effects:

  • Substances can cause cancer in humans and animals.
  • Varies between species; US EPA attributes 35-55% of outdoor air cancer risk to VOCs in the US.

• Non-Carcinogenic Effects:

  • Affect respiratory, digestive, and nervous systems if above certain endpoints.
  • Endpoints vary widely between compounds and exposure pathways.

• Odour and Annoyance:

  • Malodorous properties can irritate or annoy humans.
  • Odour threshold describes the minimum concentration necessary to be detected, often below toxic levels.

Environmental Effects of VOCs

• Ozone Formation Capacity:

  • Ground-level ozone (O3) formed through photochemical oxidation, impacts human health and plants, and is the primary component of smog.

• Particular Matter (PM):

  • Includes solid particles and liquid droplets in the air, with PM2.5 and PM10 being common.
  • Elevated concentrations result from natural emissions and pollutants, influencing health and environment.

Examples of VOCs

• Benzene:

  • Boiling point: 80.1°C
  • Sources: Tobacco smoke, solvents, paints; known cancer cause.

• Tetrachloroethylene:

  • Boiling point: 121.1°C
  • Sources: Dry-cleaned fabrics; suspected carcinogen.

• Toluene:

  • Boiling point: 111°C
  • Sources: Solvent, perfumes, detergents.

• Trichlorofluoromethane:

  • Boiling point: 23.8°C
  • Sources: Refrigerants, fire extinguishers; ozone-depleting (banned).

Sampling and Analytical Methods

Sample Matrices for VOCs Analysis

• Air: Indoor and outdoor, mobile and stationary sources.
• Water: Wastewater and drinking water.
• Soil/Sediment
• Products: Wooden boards, hairspray.

Types of Sampling Methods

• Active Sampling:

  • Uses sample collection media connected to a sampling train with a pump; involves known flow rate.
  • Components: Inlet, sampling media (tubes/bags), tubing, pump.

• Passive Sampling:

  • Sample collection media passively diffuses air; allows longer sampling without overloading media.

Canister Sampling

• Modes: Grab (short interval) and Integrated (extended period).

Direct-reading Devices

• Types:
  • Colorimetric Devices: Color change indicates VOC concentration.
  • Electronic Direct Reading Instruments: PIDs, FIDs, MOS, and Photoacoustic Infrared Detectors.

Accreditation

What is Accreditation?

• ISO/IEC 17000 Definition:

  • Third-party attestation related to a conformity assessment body demonstrating competence in specific tasks.

• Hong Kong Accreditation Service (HKAS):

  • Accreditation body in Hong Kong under the Innovation and Technology Commission.

Benefits of Accreditation

• Formal recognition of competence, demonstrating capability to meet standards and practice.
• Voluntary participation, no statutory requirement in Hong Kong.
• Provides assurance of competence to customers and authorities, benefiting the community.

Thank you!