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Quality Air by John Herbert
25 August 2004

John Herbert, hong kong energy saving expert, BEAM expert
John Herbert

A Real Problem

note this is 2004 article

The air pollution levels over the last week have soared, with the Air Pollution Index (API) breaching the 100 danger level, and the obligatory finger pointing commences.

However, not wishing to bore you with the benefits of free and cheap renewable energy, this article is focusing a bit closer to home, in fact you are probably sitting their right now - your workplace.

Contrary to media reports, the EPD reported on 19th August 2004, that the primary reason for the reduced visibility was abundant RSP in the atmosphere.

RSP for the uninitiated, is an acronym for Respirable Suspended Particles. As the name implies these particles are of a size that can be inhaled deep into the lung. It takes no special effort to inhale RSP, if they are in the air, they are filling your lungs as you read. Typically, any particle between 1-10 microns is classified as RSP.

You may also read banter reading quoting PM2, PM5, or PM10 - refer to the physical size of the particulates, PM2 has size of 2 microns. Presently EPD measure total RSP, and don't differentiate according to size.

RSP's are primarily created during the combustion process, the product of combustion include RSP, primarily due to incomplete combustion of diesel fuel.

Other contaminants, including the less well know particles such as atomised water droplets containing Legionella would fall into this category too. However, here in Hong Kong most of the RSP's that are blocking the harbour view where created during the combustion process.

Cause for Concern

RSP are particularly concerning because they directly, and in some cases terminally, affect your health.

It is widely documented, but rarely publicised, that breathing air contaminated with RSP directly causes increases hospital attendance, respiratory and a major causative factor for life threatening illnesses. Studies by The University of Hong Kong amongst others, provide a direct correlation between increasing morbidity and poor air quality. Certain professions are more at risk than others, but we don't generally spend that much time outdoors in the summer so what is the problem?

It is not widely reported, that when the outdoor air is unhealthy, the indoor environment including your workplace is equally so. The same RSP that caused ships to collide in the harbour are also circulating in your workplace air.

air pollution, hong kong, low viz, IAQ

Rushing into your office or workplace, whilst certainly cooler, it is not a sanctuary, often we find the indoor RSP concentration is double that of outside, and exceeds WHO objectives - indoors we just can't see the pollutants with the naked eye.

There are a number of chemicals that may constitute part of RSP. Two particularly important constituents are lead and aromatic hydrocarbons.

Constituents of RSP may include; Silicon, Aluminium, Calcium, Manganese and Iron, Vanadium, Nickel, Cadmium, Carbon, Lead, Bromine, hydrocarbons, Sodium, Chloride, magnesium, and Potassium Nitrate, Sulphate or Ammonium in varying concentrations depending on the source. To view a typical analysis from EPD click here


In almost every commercial office building and shopping mall in Hong Kong, outdoor air is drawn into air-conditioning equipment, mixed with room air, cooled and circulated in the occupied space. Generally the recirculate and mixed air is not filtered.

Although the outdoor air is 'filtered', one should take a closer look at the unit. Over the last twelve years I have looked at thousands, the typical commercial building filter efficiency for removing RSP is pretty much close to zero.

Therefore, outdoor air complete with RSP are drawn into our air-conditioning systems and subsequently distributed throughout the building.

Certainly, some RSP are trapped due to impingement (sticking to other trapped particles in the filter) however because of their minute size, RSP circumvent standard air filters.


Is there evidence to support the theory? You might be surprised to learn that the Hong Kong government indoor air quality survey provides an independent source for reference.

IAQ - RSP circulate in your workplace

The government funded independent study found that more than 30% of buildings investigated suffered from poor indoor air quality. And managers wonder why employee's are absent so frequently?

However, if we further consider the buildings surveyed a different picture emerges. Most buildings included in the survey were government owned buildings, Grade A commercial buildings, and other quality buildings, where one would expect an exemplary and pro-active maintenance activities.

However, most buildings in Hong Kong fail to meet that criteria, and are generally of a lesser standard, without maintenance crews. Therefore, it is reasonable to believe the that the reported thirty percent (30%) is the low end of a range that in reality extends to well above fifty percent (50%).

These would include premises using the ubiquitous window type units air-conditioning units, since these units have no outdoor air filtration whatsoever.

The government has estimated the cost of poor indoor air quality at about three billion Hong Kong dollars) per year, undoubtedly the real cost is higher.


Considering that a typical working day equates with two hour outdoor exposure and eight hour plus workplace exposure, it is clear that workplace improvements will have a significant impact on your health.

Presently, under the current Building Regulations Ordinance Cap. 123 (Fire) combustible materials are prohibited.

Therefore solutions need to satisfy both regulatory and function needs, namely non-combustible, significantly reduce contaminants including RSP, and ideally low maintenance.

About the Author

John Herbert is a veteran chief engineer with more than 30 years international engineering experience, educated in the United Kingdom, he has worked in the United Kingdom and then across Asia for more than two decades engaged by international and local companies. He is a Hong Kong Registered Energy Assessor (REA), a BEAM Professional, and stationed in Hong Kong.

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