Confined Space Ventilation
| We offer a variety of blowers and associated options for use in confined space ventilation. The RamFan products from Euramco are evolutions from traditional blowers, and offer features tailored to the buyer looking for a premium solution to their ventilation needs. Choosing a Confined Space Blower is an important part of a complete Confined Space Entry package. The fans from Allegro and ECKO are targeted to the cost conscious customer. Allegro also offers several different types of air movement options, including venturi blowers and carpet dryers. | ||||||||||||||
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| In general, it is a good idea to ventilate a confined space before entry and to maintain forced ventilation while the space is occupied. Forced ventilation is required to remove air contaminants, provide oxygen and to keep the air as clean as possible. Where feasible, it is best to blow air into the confined space and draw it out simultaneously. This approach generally requires two or more openings, and 2 or more blowers. With a confined space that has only a single entry point or when only a single fan is available, air should be blown into the confined space. A flexible duct is helpful in directing the air to the bottom of the confined space. This should get you the best purge through the space. It is important that the fresh air intake not be contaminated. In some cases, a portable gasoline powered generator will be used to power the ventilation blower(s). The generator should be located as far as possible from the fan air intake. Motor vehicles or other internal combustion engines should not be allowed to operate with their exhaust pipes located near the air intakes. Constant monitoring with a Confined Space Gas Detector should alert you to this condition, but it is good work practice to prevent the problem in the first place. When ventilating, it is important to have a rough idea of how large (volume in cubic feet) the confined space is that you plan to enter. Then, check the capacity rating of the ventilation fan, once again in cubic feet per minute. Many manufactures rate their blowers without a duct (free air) and then with a duct. Remember, you will likely have 1 or more 90 degree bends in the ducting. These will further reduce the airflow. When using forced ventilation, a good rule of thumb is at least 20 air changes should be provided per hour (once every 3 minutes). Here is an example of a confined space with a single opening and a single blower: An underground fault is 10 feet wide by 10 feet high by 10 feet long. Multiplying these three dimensions yields 1000 cubic feet. The fan to be used is rated for 500 cubic feet per minute. After accounting for duct length and bends, we get an estimate of 333 cubic feet per minute. Thus it will take the fan 3 minutes to ventilate the confined space. Since it is always best to err on the side of caution, please consider this the minimum number of air changes. The space should be checked with your Confined Space Gas Detector before ventilating, again after 10 minutes or so, and then constantly while personnel are inside. These measurements should be taken at the bottom, middle and top of the space. Some gases are heavier (or lighter) than air and so can stratify. The ventilation should keep the air stirred up, preventing this condition. Ideally the worker(s) will be wearing a gas monitor at all times. |
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