Skip navigation
All Places > NFPA Today > Blog > Author: david.hague

NFPA Today

9 Posts authored by: david.hague Employee

According to the Farmers Almanac, this winter will be freezing, frigid and frosty with wide temperature swings reminiscent of a Polar Coaster. Here’s how you can prepare your building’s fire protection systems to cope with the cold.

Wet pipe systems as their name suggests are filled with water and we know that water will freeze when temperatures drop below 32°F (0°C). And when water freezes it expands and can cause cracks in the pipe or fitting in which it resides. If any part of your wet pipe system is exposed to freezing temperatures, the system should be equipped with a heat trace system which is one accepted method of freeze prevention. Heat tracing is simply an electrical conductor which produces a small amount of heat when electricity is passed through it. This heat is usually sufficient to prevent a pipe, fitting or sprinkler from freezing. It is important to have this system inspected to ensure that it is functioning, is not damaged, and pipe insulation is intact. Follow the manufacturer’s instructions for inspecting this type of system. (NFPA 25: 5.2.7).

Another method of freeze protection is to add liquid anti-freeze to the piping system which is very similar to the anti-freeze that is in your cars radiator. Anti-freeze solutions should be tested to make sure that the mixture will not freeze at the lowest anticipated temperature. If the mixture is not correct, replacement may be necessary, be sure to use a listed anti-freeze solution. Your sprinkler contractor can complete this test very easily. (NFPA 25: 5.3.4)

Where heat tracing or anti-freeze is not practical, a dry pipe system is normally installed. As its name suggests, the piping in a dry pipe system is not filled with water but is pressurized with air or nitrogen gas. Unlike a wet pipe system where the pipe can be installed level, the piping in a dry pipe system must be pitched to drain automatically. This can result in trapped sections of pipe which must be drained manually. To drain a system manually, a drain connection called a drum drip or simply low point drain is installed. This type of drain assembly permits releasing accumulated water without releasing sufficient pressurized air to trip the dry pipe valve. Water that accumulates in the system (due to condensation or testing) should be removed before freezing temperatures set in. In Figure 16.10.5.3.5 from NFPA 13 (below), close valve “A”, remove the 1” (25 mm) plug, open valve “B: until all moisture has drained. Close Valve “B” and open valve “A”. Repeat this process until all moisture has been removed. (see NFPA 25, Chapter 13).

Where a dry pipe, pre-action or deluge system is installed, the system control valve must be installed in a heated enclosure. This enclosure must be heated since water is always present in the bottom of these valves and of course in the supply main. Now is a good time to test the heater and verify that adequate heat will be provided when the temperature outside drops. (see NFPA 25, Chapter 13).

Don’t forget the outside of the building! This can include a number of things such as hydrants and water tanks! We very rarely think about hydrants until they are needed but now is a good time to flush that hydrant and get rid of any debris inside. More important, take note of how well (or how poorly) the hydrant drains. In cold climates if the hydrant has to be used and does not drain properly it will freeze. (NFPA 25: 7.3.2.3) On the subject of hydrants, now is also a good time to flag that hydrant so it can be located when the snow piles up high. (NFPA 1:18.5.10.2). Don’t forget some clear space around the hydrant after the snow starts falling. A good guide is 36 in. (900 mm) all around the hydrant and 60 in. (1500 mm) in front of the steamer connection. (NFPA 1:18.5.10.2).

If your system is supplied by a water tank, for most locations in the US, that tank must have a heating system. Is the heating system functioning correctly? (NFPA 25:9.2.3) The temperature of the water inside that tank is required to be maintained at 40°F (4°C). Low and high temperature alarms are required to be tested prior to the heating season. (NFPA 25:9.3.3 & 9.3.4). This is important because the tank is sized with a specific amount of water based on the calculated system flow and required discharge duration. If substantial ice builds up inside the tank, the ice will reduce the amount of available water from this required amount of water not to mention the possibility of damaging the tank itself.

Speaking of ice buildup. If your fire protection system is supplied by a pond or other natural or man-made source of water, does that water source freeze over? If it does, is there sufficient water left once frozen to meet the fire protection system demand? NFPA 24 is being revised to address such issues in Chapter 5 “Water Supplies”. The proposed revision includes a method for determining ice thickness to make sure that sufficient water is left over for fire protection purposes. It may be time for an evaluation to ensure that your natural source of water has sufficient capacity during the winter months.

Remember, according to NFPA statistics, 10% of sprinkler system failures are due to lack of maintenance and 7% of failures are due to damaged system components. With a little care these types of failures can be avoided when the temperature starts to drop!


What on earth is a breeching valve?


A breeching valve, also known as a safety shutoff valve or excess flow valve, monitors pressure and flow in a system. Upon seeing excessive flow, the valve will automatically close, essentially shutting off or “breeching” any flow to the system.

 

This safety feature works very well when a piping system is used for transporting hazardous materials such as petroleum, gas, or chemicals. It is also effective in pollution control applications. Breeching valves, however, are also finding their way into other systems including fire protection systems in high-rise buildings. At first glance, this may cause some concern since the fire protection community has spent a great deal of time and effort to ensure that control valves are OPEN at all times. NFPA statistics, however, show us that although sprinklers are exceptionally effective, the number one cause of system failure is, and has been for quite some time, due to a shut valve.


taken from NFPA U.S. Experience with Sprinklers report

 

So what are the benefits of installing a valve that will intentionally close upon excessive flow? Before we answer that question, we need to define excessive flow.


What is considered excessive flow? A sheared riser, leaving an open-ended pipe, is certain to cause excessive flow. A failed fitting on the upper stories of a building might also result in excessive flow. If we wanted to, we could come up with a list of other potentially catastrophic failures, but the real questions we should be asking are, “How often do such failures occur and should we design for them?”


Keep in mind, NFPA standards are minimum standards and such design concepts are usually left up to a risk management approach.


But, let’s just assume that an excess flow valve is going to be installed in a sprinkler system. How would excessive flow be defined? We calculate flow for sprinklers on every project so determining flow is already part of the design process. For example, a light hazard occupancy can be calculated at a density of .1 gpm/ft2 applied over an area of 1500 ft2. If we do the math quickly, we see that.1gpm/ft2 x 1500 ft2 = 150 gpm. If we add 20% for balancing, a conservative figure will result in a total flow of about 180 gpm. So, would we say that anything above this number is considered excessive flow? Of course, this number is based on the traditional concept of “remote area” or can be better identified as the area furthest away or space creating the highest-pressure demand on the water supply. The idea is that if we can supply that area of the system, we can supply any area of the system.


Now, did you notice that I used the words, pressure demand? How would things change if it was flow demand?


Let’s delve into some “what if” cases here. What if the operating area took place immediately adjacent to the riser? What if we calculated the system using an actual “C” value and not the 20 or so year old “C” value required by NFPA 13? For example, new steel pipe has a “C” value of closer to 140, whereas NFPA 13 requires a “C” value of 120 for wet systems. What if we calculated based on a zero cushion or calculated based on what the actual water supply will deliver? NFPA 13 does not require such a calculation but NFPA 16 does for the purpose of determining the reduced duration of foam concentrate. The difference in flows between those two calculations can be significant. What if there are hose racks or a standpipe system involved? No doubt, that could create a significant, variable water demand.


At this point in time, NFPA 13 does not address the issue of excess flow valves. It neither permits nor prohibits the installation of such valves; there is essentially no guidance given on the subject. As revisions are being made to NFPA 13 for the 2022 edition, perhaps it is time to look at the installation and application of these valves? For example, the standard could provide guidance on how much water is too much? Is 50% over the calculated flow the right setting? What should be done about inspection, testing and maintenance? Should breeching valves be prohibited altogether? The correlating committee for NFPA 13 will be looking at these issues in depth during their upcoming meeting in December. In the meantime, if an excess flow valve is specified for a project, the best course of action is to discuss the situation with the project engineer and fire marshal to determine what the proper settings should be and whether the valve is essential in the first place.


As noted previously in this piece, the number one cause of sprinkler system failure is a shut valve. Do we really want to install a valve that will intentionally shut off the water supply to a sprinkler system?”

 

In my recent NFPA® Live session I covered the challenges of managing the high pressures needed in the standpipe and sprinkler systems in high-rise buildings. This included various techniques related to the following: moving water to the upper floors of a high-rise building, helping prevent exposure to firefighters and system components from the dangerously high pressures in a standpipe system, accepted methods of water storage in high-rise buildings, and how certain pressure regulating components work and how they are used.

I received this follow-up question from a member. I hope you find some value in it.

NFPA Live is an interactive video series in which members of NFPA staff address some of the most frequent topics they receive through the Member's Only Technical Question service. If you are currently an NFPA Member you can view the entire video by following this link. If you're not currently a member, join today!

Photo Courtesy of Liberty Mutual Insurance. 

Impact of freezing temperatures on sprinkler pipe. This ice plug was found in a sprinkler system in a freezer however,

pipes in cold areas of an unheated building could produce similar results.

 

The issue of temperature frequently comes up in discussions about sprinklers and sprinkler systems. Here at NFPA, we receive a great deal of questions related to the exposure of sprinkler systems to potentially freezing temperatures. So, given the time of year and declining temperatures across the country, it seemed like a good time to get cozy with sprinkler freeze-prevention methods.


When water freezes, it expands and can cause damage to pipe and fittings, and yes even to sprinklers themselves. Over the years, the solution to the freezing problem has been to use a dry pipe system, a preaction system, or some combination of the two. The costs associated with installing a dry pipe or preaction system; however, can be prohibitive and the price tag for maintaining these systems can be equally daunting so be sure to fully understand the advantages, disadvantages and bottom line for these solutions.


Then there’s the option of heat tracing. This approach is not as simple as it may appear to be, and may not be the best protection method because of the need for insulating the pipe and electronic supervision of the power to the heating element.


In recent years, the environmental problems associated with anti-freeze systems have been well-documented. Since 2013, NFPA 13 has limited the use of anti-freeze solutions to listed solutions only. There have not been any pre-mixed or concentrate solutions for anti-freeze in fire protection piping listed - until recently. NFPA employees are not inclined to provide specific product or manufacturer recommendations; however, a quick search for “Listed Anti-freeze” on the UL web-site shows a product that is currently available and capable of protecting piping in cold climates - so anti-freeze is making a comeback!


Whatever product or solution you decide to use, it’s important to remember to closely follow the listing and manufacturer’s instructions. Guidelines vary from product to product and often times vary from previously accepted practices. Misusing a listed product can be as dangerous as using an unlisted product; so be sure to use the right option and apply the right knowledge for maximum benefit and safety.


For example, NFPA 13 requires the use of an expansion chamber when using anti-freeze in a sprinkler system because fluids expand and contract due to varying temperatures. Figure 8.6.3.3 of the standard illustrates the appropriate arrangement of the expansion chamber and a backflow preventer (where required); while the manufacturer’s instructions should be used to determine the size of the expansion chamber. There are limitations to using anti-freeze in a system. System volume and limitations on the classification of occupancy or sprinkler type need to be considered. When using these chemicals, it is critical that the manufacturer’s instructions and listing limitations be followed.

 

As meteorologists warn, “Baby, it’s cold outside” and water cooler conversations center around tumbling temperatures – keep in mind that frigid weather can have a brutal impact on sprinkler systems. Look at systems, solutions, and safety in totality to ensure that the refrain, “Baby, it’s cold outside” is not followed by “darn, it’s wet inside” due to pipes bursting or sprinkler systems malfunctioning!


The issue of temperature usually comes up in any discussion of sprinklers and sprinkler systems, and NFPA receives a great deal of questions related to the required temperature rating for sprinklers. This is important because any sprinkler that is located too close to a source of heat can result in an unintended activation. For many years sprinkler designers have known that a sprinkler located next to a unit heater, for example, must be either a high temperature rated sprinkler if located within a 7ft (2.1 m) radius around the unit heater, or an intermediate temperature sprinkler if located in the discharge pattern of the unit heater out to a distance of 20ft (6.1 m) (see Figure 8.3.2.5). There are many other examples of where a higher temperature rating is needed for sprinklers, such as in unventilated attic spaces, under skylights, or in unventilated show windows, etc.


Up until recently, all sprinklers within a building were required to be of the ordinary temperature rating unless located near one of the above mentioned heat sources, so it is not uncommon to have a variety of temperature ratings for sprinklers within the same building or sprinkler system. However, beginning with the 2010 edition of NFPA 13, ordinary and intermediate temperature sprinklers are now permitted for use throughout a building. Why the change? Many buildings are designed without the traditional dropped ceiling, leaving an unfinished space which incorporates a large number of Heating, Ventilation and Air Conditioning (HVAC) diffusers. The diffusers drive the need for a significant number of intermediate temperature sprinklers in addition to ordinary temperature sprinklers within a system. To accommodate such installations, the sprinkler committee decided to allow ordinary or intermediate temperature sprinklers throughout a building. Now that quick response sprinklers are required and with the knowledge that the activation time between the two temperature ratings is not significant, either temperature rating is allowed. Can we mix temperature ratings within the same building? Absolutely, although it is best to use the same temperature rating throughout if at all possible. Doing so makes the replacement of sprinklers at some point in the future a simple effort.

 

Another factor to consider is how sprinklers are stored and treated before and during installation. If a sprinkler system is being installed or roughed-in in a building under construction, the sprinklers can be exposed to an untreated space inside the building. If the temperature during construction is above 100°F (38°C), ordinary temperature sprinklers will be exposed to a temperature for which they are not rated (see Table 6.2.5.1). This situation can stress the glass bulb and cause unintended operation at a later time. This has already occurred in some parts of the country and is an on-going concern whenever an area experiences a heat wave.


Suppose the temperature where you live and work does not exceed 95°F (35°C); consider where the sprinklers might be stored in such situations. A box of sprinklers is usually labeled “Store in a cool dry place” by the manufacturer. Placing a box of sprinklers in a Conex box (a large metal storage container frequently used on construction sites) on a job site in the sun in 95°F (35°C) temperatures will expose the sprinklers to temperatures of 120°F (49°C) or more. This temperature is much too high for ordinary temperature sprinklers and is approaching the threshold for intermediate temperature sprinklers.


Sprinkler temperature ratings are designed for very specific uses. Treating sprinklers properly before and during construction is important to ensure that they operate only when needed. Baby, it’s hot outside, so avoiding heat stress is important for you and sprinklers!

Bed bugs have been around for thousands of years and were thought to have been eradicated in the developed world around 1940. However, since about 1995, there has been a resurgence, most likely due to a number of reasons such as the banning of certain pesticides and an increase in international travel.


So, what does this have to do with sprinklers, you may ask? Well, one of the treatment strategies recommended by the National Pest Management Association (NPMA) to rid an area or room of a bed bug infestation is the use of heat. As a matter of fact, a temperature of 113°F (45°C) is needed to kill most bugs in a living area, however that temperature would have to be maintained for several hours and might not take care of the problem entirely. A temperature of 122°F (50°C) is necessary to eradicate all life stages (bugs, nymphs and eggs) and only needs to be maintained for about one minute, which seems to be the more cost effective approach. Some companies are even suggesting a temperature range of 130°F to 160°F (54°C to 71°C).


Why is this a problem? As you may already know, sprinklers are heat sensitive devices that, when exposed to certain temperatures, are designed to activate and discharge water to control or extinguish a fire. Even when exposed to heat from sources other than a fire, sprinklers can and will activate and discharge water. The typical discharge from a single sprinkler can range from as little as 15 gallons per minute (gpm) [57 liters per minute (lpm)] to as much as 60 gpm (230 lpm)! This flow rate might be desired if your building is on fire, but for an unintended activation, that’s a lot of water!

 

So, regarding temperature, how much is too much? NFPA 13-2016 “Standard for the Installation of Sprinkler Systems” tells us in Table 6.2.5.1.


 

As you can see in the Table, when ceiling temperatures exceed 100°F (38°C), ordinary temperature sprinklers (the type typically found in most buildings) are susceptible to activation. Even if the sprinklers do not activate immediately, the glass bulb or fusible link could be stressed, causing the sprinkler to activate at a later time.


There are a few methods that can be employed to avoid exposing sprinklers to heat. The pest management industry is addressing this problem with the development of sprinkler covers that either shield the sprinklers from excessive heat or contain a small amount of water that is frozen and placed over the sprinkler to keep it cool during the heat treatment process. Another manufacturer suggests using ice packs in their cover to keep the sprinkler cool during the treatment process. It is unclear how these covers and coolants will affect sprinklers, since these methods have not been evaluated by the usual testing labs. None of these devices presently indicate any type of listing or approval.


A more traditional method for dealing with the heat treatment process involves an impairment program as required by NFPA 25-2017 Standard for the Inspection, Testing and Maintenance of Water Based Fire Protection Systems. A system impairment involves closing the water supply valve to the sprinkler system, draining the water from the system and either leaving the system impaired for a short period of time or removing the sprinklers in the affected area and plugging the outlets temporarily so that the sprinkler system can be turned on while the heat treatment process is completed. The latter method will maintain protection in areas not being treated for bed bugs, although the impairment program will require either some form of temporary protection such as a fire watch with an extinguisher or some other method for providing temporary fire protection (a charged hose line from a standpipe perhaps) when using either method. For detailed information on system impairments, see NFPA 25, Chapter 15.


Keep in mind that once sprinklers are removed from a system, they must be replaced with new sprinklers; the old sprinklers cannot be reused (see Section 5.4.1.1 of NPFA 25). The traditional method of system impairment can be costly and will most likely involve a licensed sprinkler contractor to complete the work in addition to the pest removal contractor, but this will ensure that the bed bug infestation problem has been solved without compromising fire protection. The new covers that are recommended by pest control contractors are a nice idea, but testing should be done to verify that they work as advertised and will not compromise the operating element of the sprinkler. Regardless of the method used, this is not a (Do-it-Yourself) DIY type of project!


Be safe, sleep tight, and don’t let the bed bugs bite!

During the First Draft Meeting for the 2016 edition of NFPA 13, Standard for the Installation of Sprinkler Systems the Correlating Committee for NFPA 13 instructed all Sprinkler Technical Committees to develop a plan for streamlining the standard to make it easier to follow; indicating that there are redundancies throughout the standard that have increased the length of the document without adding clarification of the requirements. Since that time a reformatting task group has been diligently working to completely reformat NFPA 13 to follow the logic behind designing a sprinkler system.

 

In my recent NFPA live session I discussed many of these formatting changes. I received this follow-up question from a member. I'm sharing it here with you. I hope you find some value in it.

 

I'll also be offering a full webinar tomorrow, Thursday, July 19, 2018 at 1:00-2:00 pm EDT on NFPA 13, 2016-2019 Changes. This webinar is open for free to all who register. Be sure to join me!

 

NFPA Live is an interactive video series in which members of NFPA staff address some of the most frequent topics they receive through the Member's Only Technical Question service. If you are currently an NFPA Member you can view the entire video by following this link. If you're not currently a member, join today!

NFPA 13 is undergoing a major re-organization to improve usability of the standard. This presentation will discuss the initiative, progress made to date, and will outline the new format of this standard.
 
Last week I covered this topic during my NFPA Live, an exclusive for NFPA Members. During the live event I got this follow-up question. I hope you find some value in it.

---

NFPA Live is an interactive video series in which members of NFPA staff address some of the most frequent topics they receive through the Member's Only Technical Question service. If you are currently an NFPA Member you can view the entire video by following this link. If you're not currently a member, join today!

residential sprinkler, campus fire safety

As of this writing, students have moved into their dormitories, orientation has been completed, safety meetings have taken place with the RAs so residents of the dorm understand what to do in the event of an emergency. Students are now ready to face the school year. If you're a building owner or project manager, sprinkler system contractor, maintenance professional or enforcement official who oversees dormitory properties: are your sprinklers ready, too? As we honor Campus Fire Safety Month, now is a great time to inspect and test these systems.

 

On many campuses, dorm buildings have sat dormant for the summer so very few issues need to be addressed (some cleaning, some painting perhaps) to gear up for the upcoming semester. For other buildings however, construction projects (new or remodels) are wrapped up and commissioned but is everything really done and accounted for? When it comes to sprinkler systems of course, the most important issue is the water supply valve open, thus maintaining water pressure in the system? We know that sprinkler systems perform exceptionally well but when they do fail, the majority of system failures are caused by a water supply control valve that is shut. Are the valves open?  Next, have alarms (both waterflow and supervisory) been tested and verified as functional? These tests are usually stringently enforced and buildings cannot be occupied until the tests are completed.  But there is much more to sprinkler system performance that may not be as obvious. 

 

Beyond the system valves and alarms, my biggest concern has always been, “What is the condition of the sprinklers in the system”?  Frequently the sprinklers themselves are overlooked. I have personally seen sprinklers in a wide variety of occupancies (including dorms) that are covered with dust, painted, corroded, obstructed or generally neglected. What can be done about this?

 

Let’s start with testing; not flow tests or alarm tests, but an actual sprinkler performance test that is completed in a laboratory setting. Did you know that a sprinkler sample is required to be removed from the system and sent to a testing laboratory periodically? The sprinklers typically found in a residential environment (quick response and residential sprinklers in particular) need to be tested after 20 years of service and that test needs to be repeated every 10 years thereafter. That’s a very aggressive test cycle, much more so than for standard response sprinklers that are usually installed in a much more hostile environment. The test sample should include 1% of the total number of sprinklers installed, but not less than four.  Have you sent a sample of the sprinklers installed in your dorms for testing?

 

An annual inspection, specifically of sprinklers, is required in NFPA 25-2017 Standard for the Inspection, Testing and Maintenance of Water Based Fire Protection Systems. This inspection focuses on the general condition of the sprinkler. For example, is the sprinkler damaged? Is it covered with dust, corroded or of more concern, is it painted (other than from the manufacturer – more on this later)? Is it installed in the proper orientation or has the fluid in the glass bulb leaked out? We sometimes see examples of upright sprinklers that have been installed in the pendent position or pendent sprinklers that have been installed in the upright position but, I have seen cases where even sidewall sprinklers have been installed upside down! 

 

residential sprinkler, campus fire safety

 

Installation mistakes aside, most of the other issues can be easily corrected.  Up until recently, NFPA 25 simply required replacement of the sprinkler if it is covered in dust (a very common issue).  Well, that is not always the best, most convenient or economical answer. 

 

It is very common for building owners to ask, can I simply clean off the sprinkler?  My answer to that question has always been, yes if it is just a light coating of dust that can easily be removed.  But, if the sprinkler needs to be scrubbed, using a cleaner or worse; any type of solvent, then the answer is emphatically NO!  Now NFPA 25 recognizes cleaning some light coating of dust from the sprinkler by use of either compressed air (not the industrial strength compressed air but a spray can of the same product you might use to clean your computer keyboard) or a vacuum. Just be careful and do not make contact with the glass bulb.  Don’t forget, quick response sprinklers and residential sprinklers the two types of sprinkler typically used in residential occupancies are manufactured with a 3mm diameter glass bulb and they are VERY fragile!

 

What if the glass bulb is empty? Closely examine the sprinkler to make sure that it is actually empty before replacing. In some cases the colored fluid in the glass bulb may have faded due to exposure to sunlight. While loss of color might be of concern (that is how we determine the temperature rating of the sprinkler), this does not necessarily drive the need to replace the sprinkler. Tests have shown that loss of color does not affect the operating characteristics of the sprinkler, however, loss of the fluid does and this must be corrected immediately since the sprinkler will not operate.

 

And finally, painting. I think painting is one of the biggest issues affecting sprinklers. A concealed sprinkler (a sprinkler with a flat, usually white cover plate), is the easiest to overlook as far as painting is concerned. A coat of paint applied in the field can delay sprinkler operation considerably and if this occurs the sprinkler must be replaced immediately. For other types of sprinklers, however, painting may impact more than the thermal element. Any paint that adheres to the sprinkler deflector can affect the spray pattern of the sprinkler and of equal concern is any paint that is applied to the seat of the sprinkler. If the paint is thin enough, it can migrate into the seat through capillary action and cause the seat to seal tightly. The laboratory test I mentioned earlier not only tests the sprinklers ability to respond to heat but it also measures the sprinklers ability to release the cap and seal with as little as 5 psi acting on it. Should paint enter the seal and cure, the seat can adhere to the sprinkler frame and not release at all. This situation is very difficult to discern from a visual inspection and therefore, if any paint is found on the sprinkler, the sprinkler should be replaced.

 

Keeping water supply valves open and testing sprinkler alarms is critical to maintaining an operable sprinkler system. But paying attention to the condition of the sprinkler itself is equally important. Make sure your sprinklers have been tested at the correct frequency and inspect them for proper orientation, corrosion and loading. Now, it’s back to class! 

 

New to the field or looking to enhance your skills and build on your current knowledge of water-based fire protection systems? Check out our suite of training opportunities, which include online and classroom workshops. Whatever format you choose, our training will provide you with a clearer understanding of NFPA 25 so you can better protect the people on your campus. Get additional information and find the course that best fits your needs by visiting NFPA's webpage.

Filter Blog

By date: By tag: