Dust Monitor

Since dust is present in different environments and there may be different measuring tasks in priority, there is of course, a wide range of dust monitoring devices. Each user should first clearly determine the purpose the dust monitor should be purchased and the main parameters that the device should be able to determine, besides concentration (for example, air parameters or size of the particulates).

How often and where should the measurement take place?

If the dust monitor is necessary for a personal application and it is desired to apply it at different locations, then a mobile measuring device is the best solution. It is perfect for those who would like to test the cleanness level here and there, carry it and apply on demand. It is appropriate for one-time measurements as well as for the measurements at certain time intervals. For all those who search for the device for continuous monitoring, especially when it should be installed in some particular place and provide the measurement over longer time period, the stationary device is a much appropriate solution. These devices are heavier and bigger than the mobile devices, but they perform a more careful and precise measurement. Such devices are especially good for the rooms where the requirement to dust presence are very strict, laboratories, medical rooms, and the conditions are close to sterile. Dust monitors in such cases, give immediate indication that something is wrong, and there is some undesirable ingress of the particles from outside.

Compliance with the standards

Indoor air quality is an aspect covered by the international standards. Since particles present in the air may have different sizes (standard range from 0.1 to 5 μm) and different concentration, the standards, in particular, EN ISO 14644-1:2015 clearly define the limits for the rooms to be considered clean. In their turn, the devices for scattered light particle monitors applied should correspond to the ISO 21501-4 standard to be appropriate for measurements, which means meet the necessary requirements (counting efficiency, zero count test possibility, particle size, sampling flow rate) and go through regular calibration.

The main measurement method

Since there is a variety of dust monitors, the measuring principles may also vary (gravimetry or, for example, the calculation in accordance with the temperature, air pressure and flow rate), but one of the most widely spread is the scattered light principle. Exactly the devices with this method used in them have been described in the standards and a big amount of mobile and stationary devices are being designed in compliance with the requirements. In the process of the measurement, various particles may be present in the particular volume that is under check, and their size determines the power of the pulses that they are producing. In other words, light scatters off the particles when it comes against the particles, and the intensity of this scattered light is not always the same, but depends on the amount and the size of the particles present at the moment of measurement in the volume. Thus, the amount of the particles determines how the light will react and its wavelength depends on the parameters of the particles.

How to check the accuracy of the dust monitor?

Before the device is commissioned or even in the process of its application, it may be desired to check, how accurately it carries out the measurements. When it goes about dust monitors, the principle of zero count is applied. It is a kind of test, when the device is measuring an absolutely clean air. Application of a special filter takes all the particles out of the air and thus, if the device is accurate, it is supposed to show no particles detected during the set measuring time. If, in spite of the filter attached, the amount of the detected particles (especially of the bis size) is high, the dust monitor should be urgently calibrated and checked by the professionals.

Is this dust monitor an efficient particles counter?

Since dust particles may be of extremely tiny sizes, it is difficult to achieve that the dust monitor detects them all. Counting efficiency of the device demonstrates how successfully the monitor can “catch” the particles above the minimum size, determine and count them. After comparison with the reference instrument, the positive result is 50%. To meet the ISO 21501-4, the counting efficiency should be at this level or more.

Does the parameter “flow rate” matter? It does, for sure. To accurately evaluate the indoor air cleanness, the dust monitor is supposed to carry out the most precise measurements. How sensitive the device is – is an essential factor, but flow rate is not less important, since depending on these parameters, the above-mentioned efficiency may be affected. How quickly the air to be checked is drawn through the device, determins how much data will be collected over a certain time period and how quickly the required volume will be tested. It should be neither too much accelerated nor slowed down. Depending on the probe of the device, the flow rate should be correspondingly adjusted, in order to ensure the correctness of the measurement, uniform distribution of the particles and their accumulation in the sampling chamber of the device.

Is there a possibility for an error measurement?

Since the amount of the particles in the air to be measured is often beyond control and cannot be influenced, but nevertheless, should be measured, the dust monitor is designated to perform this function as good as possible. Still, some errors cannot be excluded completely, especially at high and higher concentrations of particles in the air. The light scattering method mentioned above is based on pulses scattered from the particles. When the concentration is too high, it may happen that a few pulses come against each other and cause the wrong impression, for example, that there are much fewer particles than in reality, but that they are of a much bigger size. It may be quite difficult for the device to determine this type of coincidental error, since it cannot differentiate whether the scattering happened after light striking a few small particles or one of a big size.

Does the device require storage and software?

Unless the dust monitor is used for one-time measurements, it is an advantage to have a device with a sufficient storage capacity and a possibility of software application. All the measurements can, thus, be stored for later analysis, transferred to another devices, processed, printed out, which makes the whole working process much more convenient and productive.

Important to remember

Without any single exception, all people are subject to the negative impacts of dusts. With the growing consumption of various chemical and cleaning agents, common people receive undesirable amounts of dangerous particles with the air they inhale. Any time, the sprays and powders are applied for cleaning kitchen, bathroom, furniture etc. an enormous number of particles are released into the air and then automatically inhaled. Numerous studies prove that not only people who are endangered professionally, should wear protective masks, but it is recommended to use them every time when interaction with chemical substances happens in daily life. Even though dust particles mostly are of the natural origin, it does not make them harmless. Especially it applies to those who like having pets at home, which often are an additional source of how dangerous particles get inside the houses and remain there. Since we cannot do anything about the conditions we live in and dust is the enemy that cannot be beaten, it is in our power to find the ways to submit it as much as possible. Dust monitors and similar auxiliary equipment provide a reliable help in determination of the real numbers of dust particles that surround you in your daily activities. Knowing the real state of things, it may be easier to take all the required measures of precaution, starting from continuous monitoring, wearing elementary protective elements, like masks, clothes, gloves to application of filters, good VAC systems, and carrying out regular cleaning activities in the correct way.