There are several models of equipment available on the market, but do all models meet my needs?
Following the determination of ABNT 16577 ANNEX B, mechanical ventilation is the most efficient step to control dangerous atmospheres due to the presence of toxic and flammable gases and vapors and oxygen deficiency. In addition to renewing the air, it helps to control heat and humidity inside confined spaces.
A ventilation system must ensure that air flows into and out of the confined space, by means of a blower, exhaustion, or a combination of the two systems. The simultaneous use of both blower and exhaust fan is most efficient! And it will always be easier to blow into a confined space than to exhaust it.
But even if we know that a blower is the best solution, we have to take other factors into consideration. We must consider the geometry, volume, number and size of openings in the confined space, structural interferences and existing equipment, as well as pollutants, their toxicological properties, temperature, pressure, flow, and generation point. It is recommended to adopt an adequate ventilation strategy, considering the existing atmospheric risks and the ones generated by the activity to be performed, contaminant release points and their concentrations.
For confined spaces with the presence of potentially flammable chemical agents, it is recommended that the fans, motors, electrical panels and wiring be adequate to the area classification. And it must have the proper INMETRO certification that ensures that the equipment meets this need.
Whenever you are performing services that may generate particles suspended in the air, and also in welding services, you should not use the equipment as a blower. In this case, exhaustion is the best solution for this type of operation.
One of the most important information is the air exchange according to the size of the confined space and how this calculation should be performed. You will find below a short explanation.
The equation for ventilation in confined spaces is:
Q = n × V
where
Q is the flow rate, expressed in cubic meters per hour (m3/h)
n is the recommended number of renewals per hour (ren/h); (AIR EXCHANGES)
V is the volume, expressed in cubic meters (m3). (CONFINED SPACE SIZE)
The number of air exchanges per hour still generates many doubts and we work with the recommendation based on NIOSH (National Institute for Occupational Safety and Health).
For non-classified areas, we should follow from 7 to 14 air exchanges per hour;
We should follow, for classified areas, from 15 to 20 air exchanges per hour;
In these cases I recommend that you always consider the excess flow better than the lack of flow, and the higher the flow the more air exchange in the respective confined space.
Important note: for each elbow in the 90° duct there is a flow loss of on average 15%. And this needs to be taken into consideration.
With the above information, we can already understand the need for equipment that meets the need and that there is no generic equipment for all activities. Always consult one of our specialists, who will be happy to assist you in identifying the best equipment for your operation.