Ventilation fans: 6 types to consider
Ventilation fans have come along way; here's a look at the different configurations and their best uses
Fire service ventilation practices have evolved greatly in both their applications and the equipment that firefighters have at their command. Ventilation, also known as smoke removal, has seen its stock price increase in terms of its more frequent and timelier implementation on emergency scenes.
Top-notch incident commanders are more quickly identifying the tactical need for ventilation and their firefighters are employing better equipment, in a wider variety of situations, and with more diverse tactical applications than ever before.
Negative and positive ventilation is supporting not just salvage and overhaul, but fire attack as well. Ventilating below-grade spaces for technical rescue situations and ventilating big-box occupancies like today's superstores and mega-malls are just some of the tactics used.
Improvements in fan blade design and configuration have increased the efficiency and effectiveness of today's fans and blowers without markedly increasing the overall length of the blades. This provides firefighters with better tactical airflows while overall unit sizes at manageable levels, that is, the fans and blowers will still fit into apparatus compartments and can be handled by firefighters.
Fire departments can select ventilation equipment and accessories from a real menu that better fits their operational requirements and budgets. That menu has six different power sources for the fans and four very cool accessory options.
Single-speed electric motors
These weigh 47 to 75 pounds and have an airflow of 3,200 to 12,900 CFM. This is the ventilation fan that many off us cut our teeth on in the fire service — plug it in and let it eat.
Many models on the market have moved beyond the old fan in a metal box and have incorporated designs similar to those found on their gasoline-powered cousins. These features include tilting frames, large rubber wheels and telescoping handles that make it safer to move the unit from the apparatus to the area of operation.
Direct-drive gasoline motors
These weigh 61 to 82 pounds and have an airflow of 10,300 to 19,600 CFM. The impeller on these units is mounted directly to the engine shaft, reducing the blowers overall weight.
Manufacturers have used overhead valve engines, precisely balanced impellers and vibration-absorbing feet to reduce the vibration problems — that "walking blower syndrome" that beset earlier models. Blowers using the direct-drive design tend to be more compact and provide a smaller profile for storage in most apparatus compartments.
Belt-drive gasoline motors
These weigh 79 to 155 pounds and have an airflow of 10,900 to 23,900 CFM. Belt-drive systems help absorb engine vibration, preventing the blower from walking during operation on smooth surfaces.
The belt-drive pulleys are tuned to match the horsepower and torque of the engine, thus maximizing performance. Belt drives allow the engine to be set lower in the frame, improving stability and minimizing disruption of the air flow.
These weigh approximately 75 pounds and have an airflow of 16,800 CFM. Hydraulic-powered blowers use the water flow from an attached hose line to move the fan blades.
These units are well suited for large commercial operations that may require the ventilation of hazardous atmospheres where intrinsically safe motors are needed. The smaller overall dimensions of such units, because they don't have a gasoline or electric motor, make them an attractive option for engines or pumpers and smaller departments that may not have dedicated truck companies for ventilation and smoke removal.
These weigh 50 to 75 pounds and have an airflow of 3,000 to 14,000 CFM. Explosion-proof models feature an intrinsically safe motor with an explosion-proof switch for the highest level of protection when responders are presented with potentially explosive environments.
These types of motors are compliant with UL Class I, Group D locations and provide a ventilation tool that can safely be used in most hazardous environments in either positive- or negative-pressure modes.
Moving big air
The big boy of ventilation equipment is the very high-volume, gasoline-powered positive-pressure blower. These newer workhorses in the ventilation stable come with larger fan blades than those of their more conventional kin, and deliver airflows in the 50,000 to 70,000 CFM range.
These devices — which can be skid or trailer mounted — offer incident commanders the high power ventilation capability necessary for big smoke removal and ventilation requirements posed by high-rise structures, shopping malls, multi-family occupancies and warehouses and other big-box structures.
Most of the major blower and fan manufacturers and their vendors now offer an array of accessories that can enhance the safety, effectiveness and efficiency of your department's ventilation practices. Any of the following showing up at the fire station around Christmas would surely make any truckie smile.
- Attachable light kits can turn any electric fan into a 350-watt light unit. The light kit attaches to the fan unit and save firefighters from carrying and setting up separate lighting tripods.
- Spiral duct adapters that enable more effective and efficient airflow delivery to hard-to-reach spaces, both above and below grade.
- Man-hole adapters specifically designed for placement directly over the man-hole (the one not being used for egress) so that maximum airflow is directed into the space below grade. This one is one of my favorites, having participated in many training exercise where it seemed we just could never get that fan placed correctly —and safely— to deliver the airflow necessary to keep the four-gas detector happy.
- Gas motor tachometers that attach right to the blower. The unit will read engine RPMs while the engine is running, and read total hours when the engine is off. A great tool for a preventive maintenance program for your gasoline engines.