Dehumidifiers USA

Measurement Of Indoor Air Quality

medical clean air requirements


A number of parameters are measured to determine the quality of the air inside the hospital.

Carbon Dioxide

Carbon Dioxide (C02) is a gas that occurs naturally in the earth's atmosphere, and is generally accepted as a surrogate indicator of ventilation within buildings and occupied premises.

At normal concentration levels carbon dioxide exerts an important regulatory effect in the body; it can however become an asphyxiant at high concentrations. Historically, the most common complaint expressed about indoor air quality is that of "stale air".

Typically, complainants claim symptoms of headache, stuffiness, upper respiratory tract irritation, drowsiness, lethargy and fatigue etc.

Research has shown that these symptoms tend to worsen during the course of the day, often peaking in the mid to late afternoon, but abate after vacating the premises in question.

Moderately raised levels of carbon dioxide have also been shown to reduce productivity, decision making performance, basic activity levels, information levels and crisis response - all essential for staff within a hospital, who make life and death decisions every day.

Particulate matter

The National Environmental Protection Council (NEPC) stipulates a standard for ambient particulate matter of greater than 10 microns in size (PM) of 50ug/ m3 (0.05 mg/m3) measured over a 24 hour period, with five allowable exceedances per year. QED has adopted the guideline level of 50ug / m3 for indoor air.

Raised levels of particulate matter, especially the PM|0, PM25 and PM, fractions have clear associations with increasing respiratory distress and hospital admissions, and also with worsening cardiac function and cardiac events at raised levels.

Mortality in cardiac, cancer and respiratory patients is also increased when levels of airborne particulates are high. Particulates should be controlled to prevent the worsening of these conditions within the hospital.

Carbon Monoxide

In high concentrations, carbon monoxide can be fatal. At lower concentrations, headache, dizziness and other symptoms can be present.

It is usually found when combustion products enter the airstream, for example from plant exhausts or vehicle fumes.

Carbon monoxide is an odourless gas, and can only be detected using a specialist monitor. Any detection of carbon monoxide must be investigated.


Air temperature is one of the parameters that are known to influence the thermal balance of the human body as a whole, which in turns affects the perceived comfort of the individual.

This can often be a contentious area in a hospital, as there are so many different levels of activity, from the busy staff to the bed bound patient.

Even within well maintained office spaces, temperature is one of the factors that building managers have the most complaints about.


A level of RH below 35% exacerbates and sensitizes an individual's response to airborne pollutants, and the following problems have been known to occur;

  • Dryness and irritation of eyes, nose, throat

  • Increased allergic response by asthmatics

  • Increased static electricity shocks

  • Increase rates of ozone generation

High humidity can also provide conditions favorable to the growth of micro-organisms such as Fungi or Mold and Bacteria.

Elevated levels of these microorganisms may then have negative health effects, and also cause damage to property and assets.

Volatile organic compounds

Volatile organic compounds (VOCs) are measured as a total for the air quality monitoring program, and act as an indicator that a problem may be present.

In an office environment sources of VOCs are usually from furniture, paints, and new building products.

Within a hospital, there are many more sources of VOCs, from alcohol hand rub to more toxic chemicals used for disinfection and cleaning.

High levels of VOCs usually indicate the need for more targeted investigation, and for measurement of Occupational Exposure to the chemicals in use in the area.

VOCs are a wide group of compounds, some of which can have quite serious health effects at low concentrations, and some of which are relatively harmless at the concentrations usually found in a hospital day to day.

Microbial Air quality

The levels of microbial contamination within the air of the hospital area sampled using an active sampler. No specific guidelines exist for the levels of microbes within the air that are acceptable within a building, except for those within Operating Theatres.

It is however very useful to build up a picture of the usual levels for the different areas of the hospital over time and then deviations from this can be investigated. Comparison of the levels within the building with those in the outside air are also extremely useful.

Levels of microorganisms should usually be lower inside a building than outside a building, and be of a similar species mix.

Higher levels of microbes inside that outside, or inside air reading that show a predominance of a problem species of fungus for example is a cause for concern and would require investigation.

Results should always be interpreted by a person experienced in interpreting microbial air testing results.