Rooftop RF Hazard

Cellular telephone transmission sites are most commonly found on standalone towers, however, building rooftop cellular transmission sites are becoming more and more common. These rooftop transmission sites are certainly something that all firefighters should be aware of. These sites pose a unique threat to firefighters operating on or near the roof in the form of a Radio Frequency (RF) exposure.

Most commonly the cellular transmission sites that are found on towers are made of of 3 sectors (or panels) of antennas 120 degrees from each other. Typically when they are installed on roofs, the antennas consist of 4 sectors (or panels) of antennas, one for each side of the building. Each sector (or panel) is typically made of of 3 high gain antennas, with the middle one dedicated to transmitting and the two outside ones dedicated to receiving. With the increase demand for bandwidth of today’s phones (think internet access), many cellular providers are increasing to 4 antennas per sector.

The most common frequency ranges that are found on cellular transmission sites are in the 824-849MHz, 869-894MHz and 1850-1990-MHz bands. Just for comparison, the most common public safety radios operate in the 769MHz-800MHz, 806-824MHz, and 851-854MHz range. As you can see our radios operate very close to some of the cell phone frequency spectrum, and that’s what that whole re-banding thing was all about. It is worth mentioning that our radios operate at a much lower power (3-5 watts) compared to cellular transmission sites (up to 500 watts) so there are no RF energy issues to be concerned with in regards to our radios.

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One of the most challenging parts of working around these antennas is simply identifying their presence. Often times the antennas are hidden behind fiberglass covers for aesthetic purposes. So easily detecting their presence from the street might be next to impossible. One of the only obvious indications of their presence may like one of the signs shown below posted on the stairwell door providing roof access. This sign is required by the FCC when certain levels of RF energy are present on the roof. Unfortunately this sign will not alert us when we are accessing the roof via the aerial ladder.

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There are many variables when determining the amount of RF energy that is present at each antenna site. It depends on the power output and number of radio channels or transmitters that are present at each site. The FCC permits up to 500 watts per channel, but often times only 100 watts is found in rooftop sites. For our purposes on the fireground it really doesn’t matter the actual power output. We should treat every cellular transmission site like it is capable of producing high levels of RF energy that can significantly hurt us.

The RF energy produced from these antennas is non-ionizing radiation, similar to the energy found in a microwave oven. So the major concern of RF energy exposure is over heating of the human body. Just like those leftovers in the microwave, if your body is in the path of the RF energy you could be heated to a well-done temperature. If you must be around the antenna, a good rule of thumb is to remain behind or under the actual panel of the antenna. The reason this works is because cellular transmission antennas utilize very directional antennas. Essentially all of the energy is focused out the front of the antenna. This is why being below or behind the panel is the safest place if you must be near it for any reason.You never want to allow your head to be in line with the transmission pattern of the antenna. The further away you are, the less energy you will be exposed to. It should go without saying, but never touch the actual antenna.

Besides the RF issues, these cellular sites often present other hazards such as tripping hazards and additional electrical issues. The cable trays mounted on the roof could easily be obscured by smoke causing a tripping hazard. Most radio rooms will also be serviced by a backup generator that will be independent of the buildings primary electrical system. In addition, the site will have battery backup systems as well. So it would be very difficult for us to ensure that all power has been isolated from the equipment.

One of the best things to remember when operating around rooftop cellular antennas is to simply to apply the HazMat mantra of Time, Distance, Shielding. While RF shields are available for certain applications, they have no practical use for us while accessing a rooftop during fireground operations. Simply stay as far away from the antenna as you can, and if for any reason to need to pass in front of one, do it quickly. Time and Distance can minimize your exposure.

If you are curious about the possible location of any cellular transmission sites in your area, there is a free website that will show all sites within a 4 mile radius of a particular address. It may not list every single site, but it’s pretty comprehensive and certainly seems like a fairly accurate tool for planning purposes.

 

The picture above shows a “hidden” cellular transmission site. The four squares are found on each side of the building are each hiding one panel antenna. This particular building has a total of 16 antennas, four on each side. If you found yourself operating on the roof, you could see that your head could be very close to the transmission pattern of the antenna.

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The picture above shows a two different cellular transmission setups. There are two sets of panels that are focused on side A of the building. This just shows that there are two different cellular providers on this building. You can just barely begin to see one of the panels on the D side as well. This particular style of installation is more hazardous to a crew accessing the rooftop from the aerial ladder. You would be perfectly safe to be standing behind these panels since the RF energy is focused out the front. Having said that, if you don’t need to be close to the antenna, simply stay away. Look at the windows just underneath the antenna panels, it just demonstrates how the RF energy is in fact focused straight out.

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The picture above shows another style of roof top transmission sites. This particular setup is more hazardous to the team operating on the roof. Although its hard to tell from the picture. These panels are slightly set back on the roof. This creates a situation where someone could walk directly in front of the panel and directly into the transmission beam. You can also see that the radio room structure has been added to the rooftop of the building. This style of installation would have the trip hazard from the cable trays present in-between the radio room structure and the antennas.

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Color-Coded Cribbing

Assist Chief. Dennis Baker Jr. from Baden (PA) sent in these pictures of how they set up their cribbing. He made sure to point out that Lt. Tim Firich was actually the one who should get the credit for the idea. They color-coded their cribbing based on length. The ones pictured happen to be 18” 6×6’s. As you can see in the picture below the paint color actually goes about an inch onto the side of the cribbing as well. This little addition makes it easy to visually see from a distance that the cribbing tower is square.

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The handles are 1 inch webbing cut at 16 inches long and secured with a fender washer and 1 1/4″ wood screw. They overlapped the webbing and used a soldering pencil to burn the whole for the screw. This will prevent the webbing from unraveling near the screw hole.

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The idea of color-coding could be implemented a few different ways: either length or lumber size. Even wedges could be coded with different color paint, or even a different color of webbing. For example if you painted your 4×4’s red, the 4×4 wedges could also be red, but with a different color webbing. The important thing is not of over think it. Come up with a standardized marking system that works for you and your agency.

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Building Construction Prop

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Bud Henkels from the Montgomery County (PA) Fire Academy sent in this amazing building construction prop that he built for his Firefighter Awareness to Wood Frame Construction class. The focal point of the presentation is this scale model (1 ” = 1′) that shows the students wood frame construction from foundation to ridgepole.

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On one side it incorporates modern day platform framing and on the other side, later day balloon framing. Having both different construction types present make it easy to show the differences with each style. The prop includes the ability to add a real time smoke conditions that demonstrate how differently smoke and fire can travel through each type of construction. While the prop is certainly a major part of it, the program also includes a 3-hour power point program that focuses on building terminology and other building constriction methods.

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Bud’s previous experience as a carpenter and contractor certainly shows through with this quality craftsmanship. Wile making a quality prop like this will certainly take some time; it doesn’t have to cost much money. There is a good chance that someone around your firehouse has the talent and ability to make something similar. This prop, sitting on a table in the firehouse or training room can be referred to during many formal classes, and even more importantly those informal kitchen table classes. Instead of doing some third grade quality drawing on the dry erase board; pointing something out on a prop like this would certainly enhance the learning opportunity.

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This is MY Aerial…

 

This post is not at all meant to throw stones at the recent news of multiple aerial failures. It’s also not meant to make any accusations of responsibility; rather it is just a great time to ask this question:

Who performs the preventative maintenance and inspections of your aerial device?

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Is it the departmental or municipal garage? Is it an outside vendor? Or is it you and your crews? Look back at those choices, only one group’s life is on the line… Why would the crews whose life safety depends on the aerial not perform their own lubrication and inspections of the aerial? We understand that some department’s administration may not “allow” for this to happen, but they cannot (and should not) prevent us from at least performing our own DETAILED inspection. We are not talking about simply operating the aerial on a daily/weekly check, we are talking about REALLY checking it out. When was the last time you looked at every single surface of the aerial including but not limited to: wear plates, wire rope, pulleys, hydraulic cylinders and hoses?

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Every apparatus manufacture provides detailed documentation on the lubrication process. This list also itemizes each different lube that is required for each surface and component. How do you think you mechanics learned how to do it? They read about it and were maybe shown the process by someone else. Why don’t you have them teach you how to do the same thing? Even if they wont let you take over the lubrication of the aerial, have them teach you how to PROPERLY inspect it. Ask what every simple component does; watch how the pulleys and wire rope move when the aerial is in operation. Make sure you understand everything you possibly can about this piece of equipment that rely on.

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This is my aerial. There are many like it but this one is mine. My aerial is my best friend. It is my life. I must master it as I must master my life.

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From the Jump Seat to the Front Seat

VentEnterSearch’s own Jimm Walsh will be presenting From the Jump Seat to the Front Seat on July 31, 2014 at the Third Annual Mickel Begg Leadership and Safety Conference. The conference is being held in honor and reverence to the memories of Lieutenant John Mickel and Firefighter Dallas Begg. The conference will be held in Celebration Florida from July 29 – 31 and will also include presentations by Curt Isakson, Michael Ciampo. The conference is hosted by Osceola County Professional Firefighters Association IAFF Local 3284, and the Central Florida FOOLS. All proceeds from the conference benefit the Mickel-Begg Scholarship Fund. Please click here to download the flyer for additional information and registration information.

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Roof Over

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Jamil Hudson and Brian Falls sent in this write-up and photos of something Charlotte Fire Department (NC) Engine 11 B shift recently came across during an area survey of their first due. Construction crews were in the process of remodeling both the interior and exterior of the home when E-11 noticed an obvious change of the roof structure. They stopped and spoke with a construction crew member to ask for permission to take some photos. As you can see in the photos, a second roof is being built on top of the existing roof. This construction practice is becoming increasingly popular today to modify older homes in order to reduce the costs for the homeowner or seller and to give the home a more modern and appealing look. The original roof was built on a 4/12 pitch and the newly added roof was built on an 8/12 pitch. There are several reasons why this type of roof construction can have a negative impact during normal fire ground operations. These are a few examples:

  • A false indication of possibly a second floor or an additional room despite the small window (Size-up)
  • Truck Co. operations (Vertical Ventilation) efforts may be hindered or delayed due to the double roof.
  • Initial vertical ventilation could be ineffective for interior crews during fire attack and search operations if the fire has not vented through the original roof.
  • Difficulty in locating and extinguishing hidden fire in void spaces. (Overhaul)
  • Confusion between interior crews and the outside vent crew when attempting coordinated efforts (fire attack and vertical ventilation).

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In addition, keep in mind the dimensions of lumber used, the type of roof construction and how it varies from the 1950’s to today. This particular home, the original roof joists were constructed of 2×6’s, while the new roof addition is light weight construction composed of 2×4’s. If fire has progressed rapidly, has vented itself through the original roof but has not shown itself from the new roof addition and has been burning for an extensive amount of time, what is the possibility of a collapse? If so, which of the two roof types may pose a danger of collapse, both, or maybe one before the other? What other issues could occur during a fire if this house is in your first due?

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It is imperative as the individual fire fighter and as a company, we continue to be familiar with our response areas. Learning and knowing our territories and our buildings, from the single family dwellings, the large commercial/industrial buildings, to the high rises, etc. Building construction is ever changing, when the bell sounds at 3:00 am, the everyday house fire may just be the one fire that has us scratching our heads afterwards.

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FireHouse Expo 2014

VentEnterSearch’s own Jimm Walsh will be presenting at FireHouse Expo on Thursday, July 17, 2014 in Baltimore (MD.) Jimm will have the pleasure of co-presenting a class titled Smell of Smoke with District Chief Walter Lewis from Orlando (FL) FD.

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Here is a short description of the class:

Commonly, dispatched structure fires turn out to be an odor of smoke called in by a homeowner or occupant. This program is designed to help firefighters, prospective officers or inexperienced officers determine the cause from a laundry-list of potential sources by discussing a decision-making tactic and the various sources, room-by-room in residential structures.

We’ll be in room 318 on Thursday July 17th from 08:30-10:00. We hope to see you there.

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Multi-Function Prop

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Christopher Benson from Greeley (CO) Engine 4 sent in this low cost multi-function prop. The prop is made mostly from 4×4 and 2×4 lumber that was scavenged from around the station. The prop features a forcible entry door, window bar props, a window sash, and a wall section.

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The door can be forced as an inward or outward facing door. It also features a padlock and hasp to practice defeating them as well. One of the window door props is just for observation and discussion of bars and their attachment methods, and the other can actually be forced by defeating pieces of furring strips. (Chris wanted to be sure to thank Brian Brush from West Metro (CO) for the window prop idea.) The window sash has a replaceable piece of wood as the sash so it can be defeated prior to the entering the window.

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Below that, the wall studs are placed 16 inch on center to practice SCBA low profile maneuvers. The rope simulates an entanglement from electrical wires and adds to learning opportunities. Real segments of electrical wire can also be strung through the prop to allow for cutting of the wire as an option to free from the entanglement. Since most of the materials were scavenged, this low cost prop can provide a number of different quick drills without even leaving the firehouse.

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Fortified Rear Door

Lieutenant Rich Taylor and the Crew from Winter Park (FL) Truck 61 found this door while out doing some area familiarization. From the outside this particular door shows no sign of supplemental locks. At one point there was a traditional handle, but that has since been removed and replaced with a blank. The latch is also being “protected” from a simple latch guard. It appears that a simple force with the irons would make quick work of this. This particular occupancy was a bakery, so not exactly a high profile target, or occupancy that you would expect to be highly protected. However, as you can see from the inside, nice little surprise awaits you.

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How well do you know your first due? Before this occupancy was a bakery, what was it? Perhaps some of the long time readers of the site recognize this exact door it was featured in a previous post back in November 2006 click here to check it out. However, it was a check-cashing store back then. Certainly an occupancy with that amount of cash on hand would certainly warrant having a fortified rear door.

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There is something very different about the door from the original post though… Take a look, have you figured it out? The answer will be in the first comment below so we don’t spoil it here.

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Secondary Functions

In some of our recent posts we have been sharing thoughts on the benefit of riding assignments. Part 1 of the post can be found here and part 2 can be found here.

We will now continue the discussion and introduce the concepts of secondary functions and discuss how they can be utilized to increase your efficiency and effectiveness on the fireground.

The inside team’s primary functions are forcible entry, primary search, locating and confining the fire. After the fire is knocked down and the primary functions are complete, the inside team begins to switch its focus to salvage and overhaul.

The outside team’s duties vary greatly depending on the structure and scenario at hand. On residential structures, the outside team’s priority is going to be coming off the truck thinking VES until proven that all people are out of the fire building. If there is a sign of someone home or someone outside informing us that people are trapped then VES needs to be performed. If VES is not going to be a tactic used then the outside team moves down the “ prioritization list” of functions. As mentioned earlier, the prioritization list also changes based on the structure. For example, on a residential structure VES is the main priority whereas on a commercial structure Roof OPS are the priority. Obviously the “priority” tactic may be different for each department.

Once the outside team’s primary functions of VES, Secondary Egress, Ground Ladders, Roof OPS, Aerial OPS, and OVM (Outside Vent Man) are complete they will begin to transition to more “inside” duties. Regardless of where they are operating they will still maintain the radio designation of “outside truck”. Depending on timing, if the secondary search has not already been completed, the outside team will immediately perform the secondary search. Once all searches are clear and the primary functions are completed, the outside team will also transition into salvage and overhaul duties and assist the inside team. During the salvage and overhaul operation, the outside team sets up interior lighting, establish PPV fans if needed, and begins to monitor the interior air quality.

We understand that some of the specific functions listed might not apply to your situation due to staffing or departmental buy-in. The idea here is to simply “list” all of the main functions of your truck crew and come up with some sense of prioritization for them. Obviously these won’t work for every scenario and on every structure. Some situations may need all of the tasks done “at once” which will not allow for one crew to work down the list. The idea behind listing them out and prioritizing them is so everyone operating knows what to expect, and what jobs still need to be accomplished. Simply listing riding assignments down in some SOG, or posting them on a station board is not enough. Train until every member of your department is knowledgeable and proficient in relying on riding assignments.

Officer (Inside Truck 61): Radio designation of Truck 61

  • Primary Functions: Forcible Entry, Primary Search, Locating the fire
  • Secondary Functions: Overhaul
  • Tools Carried: TIC (Thermal Image Camera), Hook, Halligan, Flashlight, or any other tools needed to accomplish task
  • In large area buildings, i.e. large commercial space, consider large area search rope kit

Firefighter (Inside Truck 61): When working away from Truck 61’s Officer, radio designation becomes Truck 61 Irons

  • Primary Functions: Forcible Entry, Primary Search, Locating and confining the fire (water can and/or closing fire room door)
  • Secondary Functions: Overhaul
  • Tools Carried: Irons, Water Can, Hook, Thru-the-Lock (Commercial Structures), Flashlight, or any other tools needed to accomplish task
  • Thru-the-Lock tool on commercial structures, i.e. “A” or “K” tool for glass storefronts. Also consider the Hydro-RAM for apartments, college dorms, doctor offices, and hospitals

Driver (Outside Truck 61): When working on individual assignments, radio designation becomes Truck 61 Tractor

  • Primary Functions: VES (Vent Enter Search), Force Rear Door (Secondary Egress), Ground Ladder OPS (Secondary Egress), Roof OPS, Aerial OPS
  • Secondary Functions: Secondary Search, Salvage, Overhaul
  • Tools Carried for Primary Functions: TIC (Thermal Image Camera), 6 foot Hook, Halligan, Ground Ladder, Flashlight, Saw (Roof OPS)
    • Consider a Striking tool (i.e. PIG, Flat Head Axe, or Sledge) and Rotary Saw on commercial structures
    • Consider longer hook based on structure (Roof OPS or high ceilings)
  • Tools Carried for Secondary Functions: TIC (Thermal Image Camera), 6 foot Hook, Halligan, Flashlight, Salvage Tarps, Interior Lighting

Tillerman (Outside Truck 61): When working on individual assignments, radio designation becomes Truck 61 Tiller

  • Primary Functions: VES (Vent Enter Search), OVM (Outside Vent Man), Ground Ladder OPS (Secondary Egress), Report fire conditions in the rear, Roof OPS
  • Secondary Functions: Secondary Search, Salvage, Overhaul
  • Tools Carried for Primary Functions: TIC (Thermal Image Camera), 6 foot Hook, Halligan, Ground Ladder, Flashlight, Saw (Roof OPS)
    • Consider 55” Halligan Bar and Rotary Saw on commercial structures
    • Consider longer hook based on structure (Roof OPS or high ceilings)
  • Tools Carried for Secondary Functions: TIC (Thermal Image Camera), 6 foot Hook, Halligan, Flashlight, Salvage Tarps, PPV Fans, Gas Monitor

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