Confined spaces are considered favourable environments for the rapid increase of contaminants or the reduction of oxygen. Most of the workers are aware of this risk. However, too often, people responsible for the installation of the ventilation are only following the guidelines to ensure compliance without asking the right questions.
“They ventilate for 5 to 10 minutes, whatever the situation, because they always did it that way, or because the procedure says so. Instead, they should perform a detailed analysis to take the appropriate decisions,” reminds Dominic Lehoux, SPI Advisor.
Beware of the nature of the contaminants
The contaminants involved must be identified. Not all of them present the same properties! Whether it is gas, smoke or dust, their current form has a direct impact on the selection of the evacuation method.
Within the gas family, properties also differ. Density will influence the recommended evacuation method. Certain gases are heavier, others are lighter than air. Even worse, certain are explosive, others not. The wrong blower may cause an explosion!
Taking into account the configuration of the confined space
Consider the shape of the confined space as well. You won’t ventilate the space the same way if it is a hole in the ground or a conduit. The wind circulation trajectory greatly influences the capacity to evacuate the contaminant.
The question of the number of openings and their position is also equally important. If there are a lot of openings and they are on top, the strategy won’t be the same as if there was only one opening at the bottom.
Each time, the nature of the contaminant must always be on your mind. A lightweight gas will be easier to evacuate if the opening is located above instead of on the bottom!
Install a ventilation system for more efficiency
The installation of the blower is seen as an easy step. However, a stupid mistake can have severe consequences! “I’ve seen the air intake of a ventilation system located near running vehicles, regrets Dominic Lehoux, poisoning workers instead of protecting them!”
Besides checking the quality of the air powered in the confined space, don’t forget to monitor the quantity getting to destination. Each 90-degree elbow in a hose reduces the power. Choose a straight line, if possible. If not, make sure to have a blower with enough power to push the air properly!
Consequently, it is difficult to assess the required time or to impose a standard. The best way to confirm the efficiency of your method is to perform gas detection again!
When in doubt… ventilate!
If you don’t detect any contaminant, Dominic Lehoux advises to ventilate anyway. “Think about the comfort of the workers, unpleasant odours or bacteria that can be found in such spaces. Contaminants are not the only thing that can bother your employees!”
You would like to offer training to your managers to make sure they provide optimal ventilation each and every time? Ask SPI!