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DAS or Distributed Antenna Systems for various purposes have existed in some form in commercial projects for nearly 20 years.  However, Public Safety DAS is a new mandated provision in most cities in the country for all new commercial projects.  It is also known as ERRCS (Emergency Responders Radio Communication System) in some municipalities.  Its purpose is to provide for an in-building system to tie into a communications network for first responders in the same city. This network essentially re-transmits fire or police radio frequencies from outside a building, where the signal is presumably stronger, into the building, where it usually is weaker or non-existent. Below we are offering detailed illustration of this system, along with typical questions developers may have in connection with this mandated provision.  



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Note: Information offered here is summarized for a quick orientation for our clients but is not offered here as a substitute for public safety mandates as detailed in documentations by the city authority responsible for your project.

National fire codes now mandate that all new and existing buildings have wireless coverage indoors for use by first responders in case of emergencies.

National Fire Alarm and Signaling Code NFPA-72 was drafted to provide the latest safety provisions to meet demands for fire detection, signaling and emergency communications. NFPA 72 requires the use of a public safety Distributed Antenna System (DAS) strictly for use by first responders.  Such system is also known as Emergency Responders Radio Communications Systems or ERRCS for short.  Public Safety DAS is installed to enable first responders within the building to communicate during an emergency. It is NOT to be confused with a commercial DAS system which provides signal from commercial carriers, such AT&T & T-Mobile.

Public Safety DAS or (ERRCS) must be on a different spectrum than commercial wireless and covers the entire building, including basements and stairwells – areas where having commercial wireless signal is NOT critical. Public safety DAS must also have backup power  in case of an outage. Critical Areas, such as a fire command center, fire pump room, exit stairs, exit passageways, elevator lobbies, standpipe cabinets, sprinkler sectional valve locations, and other areas deemed critical by the authority having jurisdiction are required to provide 99 percent floor area radio coverage.

It is important to note that there are different versions of NFPA code passed each year and individual states/cities can approve whichever version they see appropriate and some will adopt new provisions but don’t always enforce them. This means that code varies from one municipality to another and there’s not always strict adherence in some.

In fact, even the title of this mandate may vary from city to city: City of Santa Monica refers to it as “Emergency Responder Enhanced Radio Coverage System” or ERRCS. We can however advise you that as of now City of Los Angeles has a more stringent set of requirements attached to this provision than almost any other city in the country and most of its inspectors enforce whatever codes the city has adopted. Your Certificate of Occupancy in the City of Los Angeles will be withheld should these provisions not be incorporated or fail in the electrical dept inspection of it or its functionality test by the fire department. That is why we have dedicated a section here for how to approach public safety in Los Angeles.

Media Systems provides professional site surveys and engineered DAS (Distributed Antenna System) solutions powered by Comba Telecom and ADRF.  Below is a video illustration for Public Safety Systems (ERRCS):



    • A system rack is installed in a 2-hour rated space, typically on a Parking level in smaller buildings. Smaller systems may be wall mounted in the space (see Items 1 & 2 in illustration). This head-end features a radio signal sender and receiver (BDA) and its power supply. The radio is programmed to receive and send signals over frequencies required by the city. It may also be wired to an annunciator (in City of LA) that gives feedback on the status of the radio and its power supply.
    • System is wired to a roof-top antenna via a vertical pathway (Item 4) which enables the radio to communicate back and forth with first responders.
    • A horizontal wire pathway (Item 3) sends an amplified signal to indoor antennas (Items 6) which go to areas where the signal is assumed to be weak. Typically a computer with highly specialized software uses architectural plans to predicts where these antennas will be needed to overcome poor ambient signal.
Section 5 - What is Public Safety - Illustration


As mentioned earlier, the City of Los Angeles has the most stringent requirements attached to Public Safety. While all municipalities have adopted the general guidelines with regards to how much signal is required and where the City of LA has additional mandates which most of its inspectors are aware of and enforce. Currently, the following is what we know is required as of Sep 2018:

    1. If your project is required to have a Public Safety System (ERRCS), the city will require to see a submission to the city documenting several aspects of the system. This is typically performed by your subcontractor providing and installing this system. The submission will include a computer prediction map, floor by floor, showing not only all system elements but also a predicted pattern for the signal it will generate. It will also include details provided by the sub showing specs for all components and calculation for power usage and power backup time. The city will review this design (takes 3 to 5 weeks) and if approved will then require your sub contractor to pull both electrical and fire department permits.
    1. All horizontal signal pathway on garage levels (where signal is likely to be lowest) must be in red EMT conduit. Cabling used for public safety has a wide bend radius; therefore typically conduit used should be wider than 1″. In garage spaces where cabling length is over 100 Feet or has more than one bend, typically 1.5 to 2 inch red conduit is used.
    1. All Junction boxes on horizontal pathway must also be red.
    1. All Vertical signal pathway must also be in red conduit installed in a 2-hour rated space.
    1. A 24-hour battery backup must be provided and be dedicated to the system – City will actually require that your submission for a Public Safety permit to include power calculation indicating that the provided backup can in fact provide power for 24 hours given the size of the proposed system.
    1. Battery backup must have UL-50E listed housing or be housed in an enclosure with this UL listing clearly visible on the backup unit housing or enclosure.
    1. Public Safety DAS must be isolated from commercial cell DAS.
    1. Radio signal generator (BDA) and its battery backup must be enclosed in a 2-hours rated space. Typically this device and its backup are placed in a 2-hour rated space on a garage level, assuming the vertical distance from this location to roof-top antenna is less than 100 linear feet (radio signal collected from roof-top weakens over runs exceeding 100 feet
    1. Radio Signal generator (BDA)itself must be housed in an enclosure with UL-50E listing stamp visible on the device or on the enclosure housing it. Within the next year or two we may see BDAs manufactured in chassis that meet the UL-50E Listing, and therefore eliminating a need for the external enclosure we now use.
    1. System must have on-going monitoring that will give visual indication of being on, being powered and providing visible feedback on status of its battery backup. Typically this is provided via an annunciator.
  1. Conduit penetration points from a 2-hour-rated space into a non-rated space may require using a junction depending but typically your subcontractor will know where that may be required.

Link to City of LA’s most recent guideline Public Safety DAS (ERRCS) as of August 2018


Question: How do I know our new construction is subject to this requirement?

Answer: If any of the following are true of your property development, then this mandate applies to your project (Please read the actual document from the link above since these city requirements change frequently and we have limited this topic to only new construction here):

  1. There are more than 3-stories above grade plane
  2. The total building area is 50,000 square feet or more
  3. The total basement or parking area is 10,000 square feet or more
  4. Any basement or level that extends 2 or more stories below grade plane
  5. Any building that is 20,000 square feet or greater and is equipped with a solar voltaic system

Question: Our project meets one or more of above stipulations and the city inspector or departments have not asked for Public Safety provisions; does that mean we are not subject to it?


Answer: We have already seen two instances where the city inspector did not inform the developer or general contractor that a public safety system was required in a fully framed new construction. We also know of one electrical inspector actually passing and signing off on the final electrical inspection of a new building without noting that a public safety system was required or needed to be inspected, but the fire department inspector noted that in its inspection. Given the scale of work to be inspected by an electrical inspector, the lack of provisions for public safety may not even be noted. Therefore, the city electrical inspector may not even notify you that a public safety system is required in your project, but the fire department WILL know because that department’s scope of inspection of your project is far more limited and their agents will look for it when they inspect the fire provisions. You will not get a final CFO without fire department testing not only typical fire-related systems but also a Public Safety system which they will test.

Question: Our architect believes that given the small size of our building we can get a test and see if our building even needs a Public Safety system and avoid spending $50K plus for such a system.

Answer: For some reason, we hear that a lot. It is true that some smaller buildings with NO underground parking will have enough signal in the interior and escape routes for first responders to get signal. However, chances of that happening with a subterranean garage are very small and no city inspector wants to have the responsibility of deciding that you will have adequate ambient signal even on above ground levels. The burden of proof that there will be adequate signal in a building is on the owner of the project.

You also should not take the risk of completing construction without at least infrastructure for public safety (ERRCS) being in place if you want to avoid an expensive retro-installation. That is why months before a foundation is poured, a design for a public safety system should be ordered through a qualified subcontractor. That design looks at your architectural plans and some additional input related to construction type and typical materials used and will predict where antennas need to be installed to compensate for poor signal. Typically the computer-generated designs generate a conservative report that provides for more signal and leans toward more antennas that may in fact be required, because it is difficult to know the exact amount of ambient or generated signal until the construction is complete.

Essentially, the city’s means of verifying if signal requirement are being met is to see that design. If the design indicates you need to have the system, then that design and its details must be filed with the city and appropriate permits will need to be pulled. This is known as a public safety design submission to the city and typically your subcontractor performs it.


Once you determine Public Safety DAS System (ERRCS) provisions are required in your project, the first step is to acquire a design based on your architectural plans. A highly specialized software used by RF engineers will analyze architectural plans to predict where the signal may be below code. It will then create a design showing the signal pathway, junction points, and all locations requiring indoor antennas.

Public Safety (ERRCS) installation firms often provide you with a design, sometimes at no charge. However, typically such firms are likely to provide you with a design incorporating their preferred gear. The best practice for a developer is to ask and pay for a design submitted by a third party design engineering team. The developer can then ask different subs/ installers for multiple bids on the same design, rather than getting multiple bids on various designs & systems submitted by various public Safety installation firms.

Once you have selected an installation team, you will authorize that subcontractor to submit your design with their own notations on the design to the City of LA’s fire department for review. This should ideally be done prior to main deck over garage being poured in order to accommodate sleeves into the garage levels where by city code all wiring must be enclosed in red EMT conduit. This submission should take place at least 45 days prior to needing approval.

City of LA requires the design to show all pathways and location of all its elements along with heat-maps and various reports showing expected signal, all to be printed on 24×36 paper to be reviewed by a city inspector. There is no charge for the review, but once the design is accepted, the fee for review and permit by City of LA Fire Department is typically in the $700 to $1100 range. Post that approval and fee payment, there are additional fees for electrical permit and inspections. That fee will be based on the scale of the project.

No developer should allow a public safety system to be installed before the city has reviewed the design and approved it. Upon completion of the system, both electrical and fire department will inspect the system. The electrical inspector will not examine signal generated by this system but will enforce all the other electrical codes related to the system’s elements & pathways. Conversely, the fire department is primarily focused on signal generated and will test the signal upon its completion to make sure calls generated from different areas of the venue are successfully made.

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