Indoor Air Quality Monitors
Indoor Air Quality Monitors are a class of portable and fixed instruments that measure multiple indoor air quality parameters. Which and how many parameters vary by instrument. Some examples of parameters:
- CO and CO2
- Temperature
- Humidity
- Particle Count
- VOC’s such as Formaldehyde, Toluene and others found in many solvents and cleaners
- Combustion gases such as NO2, SO2, H2S
Particle Counter
Particle counters detect and count particles in the air. Not only are they useful in HVAC applications, but also for clean room environments where particles affect research or manufacturing. There are two main factors that influence the choice of a particle counter:
- Particle size. This is partially determined by the class of the particular cleanroom or customer need
- The flow rate capability of the particle counter. In order to do that we need to consider one of the formulas from the ISO standard: Vs = (20/Cnm) x 1000
This formula will calculate how many litres of air need to be sampled at each location in the cleanroom. For example, the certification of an ISO class 6 cleanroom. The largest considered particle size for this class is 5.0 μm of which the cleanroom must have less than 293 particles per m3 (see table below). So our formula will look like this:
Vs = (20/293) x 1000 = 68.3
At each measuring point, 68.3 litres of air must be sampled. If a small handheld particle counter with a flow rate of 2 litres per minute is used, air will have to sampled for 34.2 minutes at each measuring point. In this case it may be more economical to use a particle counter with a faster flow rate, minimize the time spent certifying the cleanroom.
| |
Particle Size per m3 |
ISO 15644-1
Cleanroom
Class |
U.S. STD 209E Cleanroom Class |
0.1 µm |
0.2 µm |
0.3 µm |
0.5 µm |
1.0 µm |
5.0 µm |
| 1 |
- |
10 |
2 |
- |
- |
- |
- |
| 2 |
- |
100 |
24 |
10 |
4 |
- |
- |
| 3 |
1 |
1,000 |
237 |
102 |
35 |
8 |
- |
| 4 |
10 |
10,000 |
2,370 |
1,020 |
352 |
83 |
- |
| 5 |
100 |
100,000 |
23,700 |
10,200 |
3,520 |
832 |
29 |
| 6 |
1,000 |
1,000,000 |
237,000 |
102,000 |
35,200 |
8,320 |
293 |
| 7 |
10,000 |
- |
- |
- |
352,000 |
83,200 |
2,930 |
| 8 |
100,000 |
- |
- |
- |
3,520,000 |
832,000 |
29,300 |
| 9 |
- |
- |
- |
- |
35,200,000 |
8,320,000 |
293,000 |
Beyond these basic functions, consider additional features such as pre-programmed ISO formulas and options to measure airflow, temperature, and relative humidity.
What is Indoor Air Quality?
Indoor Air Quality, or IAQ, refers to the study, monitoring, remediation, and prevention of indoor pollutants and particles that cause discomfort and even health problems in homes and businesses. In the 1980’s and 1990’s, Sick Building Syndrome became a popular term in the media. Buildings and residences have increasingly become sealed tighter with less exchanges of fresh air, so indoor air quality is more important than ever. In the U.S., indoor air quality is regulated by the EPA and OSHA, as well as individual state regulations, particularly California, New Jersey, and Washington.
Poor indoor air quality (IAQ) has been tied to symptoms like headaches, fatigue, trouble concentrating, and irritation of the eyes, nose, throat and lungs. Also, some specific diseases like asthma have been linked to specific air contaminants or damp indoor environments.
Lack of outside air is not the only cause of problems
- High or low humidity
- Recent remodeling
- Activities in or near a building that can affect the incoming fresh air
- Dust from construction or renovation
- Mold
- Cleaning supplies
- Airborne chemicals including outgassing of small amounts released over time from building materials, pesticides, volatile organic compounds (VOC), carbon monoxide, improper exhaust ventilation of ozone (byproduct of some office machinery) may cause poor IAQ.