Indoor Air Quality Guidelines in Hong Kong: Analysis for Healthcare and Public Spaces

This analysis combines the Hong Kong Indoor Air Quality Management Group's guidelines for offices and public spaces (2019) and specific guidelines for schools (2022) and retirement homes (2022). It focuses on the uniform indoor air quality (IAQ) strategies, the critical role of CO₂ monitoring, and the stringent IAQ targets.

Part 1: Strategies, IAQ Targets, and the Role of CO₂

The Importance of IAQ

In Hong Kong, people spend most of their time indoors, making indoor air quality a significant impact on health, comfort, and productivity. Poor IAQ can lead to Sick Building Syndrome (SBS), characterized by symptoms such as headaches, lethargy, and irritability, and can aggravate pre-existing conditions such as respiratory problems in the elderly and children. Hong Kong's IAQ guidelines are voluntary and self-regulatory, but are based on international standards such as ASHRAE and WHO guidelines.

The IAQ Management Strategy (Steps)

The recommended strategy for achieving good IAQ is a systematic process that should be considered at every stage of the building's life cycle (design, construction, and operation).
1. IAQ Management Program: Develop a program to identify and address problems.
2. IAQ Team: Assemble a team (building management, staff) responsible for policy, communication, and complaint handling.
3. Walkthrough Inspections: Conduct inspections at least annually to identify sources of contamination and areas for improvement.
4. IAQ Parameter Monitoring: Measure CO₂, temperature, and relative humidity as needed to verify ventilation effectiveness.
5. Education and Communication: Inform residents, staff, and visitors about the importance of IAQ and good practices (e.g., minimizing pollutants).

IAQ Targets and CO₂ Standards

Hong Kong uses two IAQ targets (Excellent Class and Good Class) that are stricter than traditional occupational health standards, as they aim to protect a broader population—including young people and the elderly.

CO₂ is commonly used as a surrogate for air freshness and ventilation system effectiveness. CO₂ levels above 1000 ppmv indicate low ventilation rates and the accumulation of other contaminants in indoor air.

Carbon Dioxide (CO₂) 8-hour, Good Class (ppmv) 1000
Carbon Dioxide (CO₂) 8-hour, Excellent Class (ppmv) 800

CO₂ measurements should be performed in areas with high occupancy densities, at fresh air intakes, and in areas where poor air quality is reported. Real-time monitors such as Non-Dispersive Infrared (NDIR) analyzers can be used for this purpose.

Temperature and Humidity

Temperature and relative humidity are crucial factors for thermal comfort and the prevention of microbial growth. The recommended optimal ranges for air-conditioned rooms are:
* Temperature: 20°C to 23°C in winter and 24°C to 26°C in summer.
* Relative Humidity: 40% to 70%.
* Mold Prevention: Humidity should be kept below 70% to prevent mold growth, which is a constant challenge in Hong Kong's humid climate.

Part 2: Controlling Sources of Pollutants and MVAC Systems

Sources of Indoor Air Pollution

The majority of pollutants originate from the indoor environment itself:
* Materials: VOCs (Volatile Organic Compounds) and formaldehyde from furniture, carpeting, paints, adhesives, and cleaning products. In nursing homes, scented products, hand sanitizers, and medicated oils can also cause irritation.
* Activities: Gases and particles from photocopiers/printers, as well as dust from chalk in schools or steam and odors from kitchens.
* Reduced VOCs: The use of carpet is not recommended in schools and nursing homes; linoleum, hardwood, or tile are recommended. Using products with low-VOC or Green Labels is essential.

MVAC System and Ventilation

Adequate and well-designed ventilation systems are the most effective strategy. * Natural Ventilation: Can supplement mechanical systems by opening windows and doors for cross-ventilation, provided the outdoor air quality allows.
* Design: Fresh air intakes should be located where the air is cleanest, away from exhaust vents, traffic, garages, and garbage disposal areas.
* Maintenance: A comprehensive maintenance schedule is vital to ensure the system performs as designed. This includes monthly filter and flushing services, and annual ductwork inspections. Improper system maintenance can lead to contamination or microbial growth within the system itself.
* Humidity control: Condensate pans and drains must be checked regularly to prevent mold growth.

Jille Kuipers, Innovation Manager at LuxBalance, on the strict CO₂ requirements:
"Hong Kong sets the standard for at-risk groups: a CO₂ level of 800 ppm in a public space is considered Excellent Class. This is a very ambitious threshold that shifts the focus from minimal ventilation to optimal air quality. The Room You 1 sensor was developed with these standards in mind. The fact that CO₂ monitoring, temperature, and humidity go hand in hand in these guidelines confirms that organizations need a multi-sensor solution to meet the needs of Excellent Class. Our portable sensor, which accurately measures all these parameters, offers the flexibility needed to support IAQ managers in their walkthrough inspections and to make thresholds visible to staff and residents."

References:
Indoor Air Quality Management Group, The Government of the Hong Kong Special Administrative Region. (2019). Guidance Notes for the Management of Indoor Air Quality in Offices and Public Places. Hong Kong.
Indoor Air Quality Management Group, The Government of the Hong Kong Special Administrative Region. (2022). Guidance Notes for the Management of Indoor Air Quality in Elderly Homes. Hong Kong.
Indoor Air Quality Management Group, The Government of the Hong Kong Special Administrative Region. (2022). Guidance Notes for the Management of Indoor Air Quality in Schools. Hong Kong.