A couple years ago I led a university engineering course covering Fire Protection Engineering.
While the students consisted of both undergraduates and a couple graduate students, we had one working professional audit the course whom I had worked with on several projects. He was a respected local plan reviewer who had nearly three decades of fire service and review experience. We carpooled to campus before and after each class and had great discussions on the profession, the course, and nuances of private versus public experiences.
One week he told me that he was very surprised by the class.
Not by the content, but that the engineering students didn’t just already know the concepts we were teaching.
It wasn’t that he thought the group wasn’t intelligent, he just always carried the premise that engineers knew all the important concepts that non-engineers don't. The realization he had after a few weeks was that each student was starting from scratch just as he had done years ago.
The concept surprised me.
While there exists a small handful of fire protection programs in the U.S., the far majority of people who work in and around the industry do not have formal degrees in fire protection. Even for those people, the most important knowledge gained is learned on the job.
The premise drives at the point that the greatest benefit to education, at least in engineering, is gathering the ability to think critically and establish a platform for lifetime learning and growth. Recent graduates, even out of the best programs, are nowhere near the same people they become 5, 10, or 15 years later.
Education isn't about the content, it's learning how to learn.
Those that don't embrace lifelong learning get passed by those who do. Degrees (and education) matter, but a degree in fire protection and/or engineering does not inherently translate to knowledge or a successful career.
There is so much great information out there; much of which is more accessible now than ever before.
Just about everything I gained during an architectural engineering undergraduate program concerning fire protection was in self-study or through internship experience.
Would an architectural engineering program have set me up for long-term success in fire protection? Absolutely; I have no doubt it would have. The many people I’ve encountered from that program (University of Kansas Alumni) or other nearby engineering programs have already proven that it doesn’t take a fire protection degree to do extremely well in this industry.
Conversely, I later studied Fire Protection through the University of Maryland a Master of Engineering graduate program. Was is all that it was cracked up to be? In my opinion: yes and more. I learned to think about fire protection as a complete entity and not just within the context of fire alarm and fire sprinklers. I developed roots in performance-based design, began to consider special challenges of nuclear power generation or marine suppression systems, and experienced a depth in content that I had not known existed.
Those two programs have impacted my life dramatically. Yet, the most important takeaway I have from each of those experiences is the ability think critically and have a fanatical willingness to continue learning.
I read recently that more content is published online in every two days than had been created in all of human history through the twentieth century. There is so much great content in fire protection that exists in printed books, in reports, in training programs, in committee discussions, or is between the ears of that colleague in the office.
Knowledge is not limited to formal education – and formal education is not a pre-requisite to be a contributing and success story in this industry.
While it might be easy for engineering graduates to say that education isn’t critical to success, I readily believe that the most important and productive learning we can gather is in non-stop reading and intentional question asking.
There is so much to learn.
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Not all code revisions are more conservative.
The 2018 Edition of NFPA 101 has updated the long-held occupant load factor of 100 sqft per person to 150 sqft per person. If you don’t live in the life safety arena, this change allows the calculated occupant load for a business space to be notably less, thereby requiring less exit width, stair width, potentially the number of exits, and other means of egress requirements.
The 1934 Building Exit Code first incorporated the density of 100 sqft per person, which was based upon a 1922 recommendation from the Building Exit code committee. It has since carried through over eight decades of code revisions and has lasted through many differences in office design.
Concentrated Business Use Introduced in 2015
The Life Safety Code introduced the Occupant Load Factor for “Concentrated Business Use” at 50 sqft per person in the 2015 Edition.
The goal with determining occupant loads has always been to provide the means of egress for a maximum probable number of occupants, and the introduced higher density was intended to address higher-density spaces than would normally be expected in a business occupancy. Annex material in NFPA 101 states that this should be applied where occupant concentrations are maximized, such as business call centers, trading floors, or data processing centers.
Modern open office concepts have changed the way we congregate and occupy buildings
Challenges with High Occupant Loads
This 2015 Edition change, according to testimony in committee hearings for 2018, has brought increased scrutiny and sometimes higher occupant loads to business occupancies by review authorities.
Increased occupant loads impact egress capacity, additional exiting, and can be very difficult to achieve higher occupant loads in existing buildings. Without additional horizontal exiting or plumbing fixtures, many existing office buildings cannot accommodate redesigns under higher occupant loads.
Open office concepts have also introduced new challenges. Collaborative spaces are sometimes being reviewed as assembly, even though these small rooms are intended and often used by the same people that are no longer at their workstations. The occupant load could effectively double-count the same occupant for two different work areas.
While terminology for the collaboration rooms is not entirely defined, modern office buildings are often labeling these as huddle rooms, quiet rooms, focus rooms, enclave rooms, or other owner-specific terms. These type spaces appear to meet the intent for the new collaborative room load factors identified below.
Collaboration rooms, often labeled as huddle, quiet, focus, or enclave rooms, are often used for smaller group activities by people who otherwise occupy the open office space. These smaller spaces function differently than traditional conference rooms.
Researching New Load Factors
The NFPA Fire Protection Research Foundation sought to study the appropriateness of the business occupant load factor for modern buildings in 2012.
Two studies stemmed from their initiative; a WPI Student Research project studies office building designs, modern changes in the workplace, and occupancy impacts of flexible employee scheduling and telecommuting. This study suggested it would be reasonable to increase the load factor to 150 sqft per person.
The second study, by Gilbert Group at the University of Canterbury in Spain, found average load factors for modern office buildings averaged 181 sqft per person. Both studies summarized that the 100 sqft per person occupant load was considered conservative.
Further testimony in the committee hearings suggested that at least ten research studies on office buildings conducted since 1935 have indicated that the Occupant Load Factor for businesses was conservative at 100 sqft per person.
The research, motions, and resulting voting brought a few major changes to the 2018 Edition of NFPA 101. Business use occupant load factor has increased from 100 sqft to 150 sqft per person; the “Concentrated Business Use” load factor has remained from the 2015 edition; and lastly small collaboration rooms and large collaboration rooms (with a threshold at 450 sqft) are given occupant load factors of 30 sqft and 15 sqft per person, respectively:
NFPA 101 Updates to Business Occupancies by Year
The new occupant load factors use the more modern net square footage (square footage inside the perimeter of exterior walls with deductions for hallways, stairs, closets, interior wall thickness, columns, and other features, NFPA 101-2018 220.127.116.11.2) instead of gross square footage.
While the discussion above considers the process for NFPA 101 Changes, the International Building Code has similar provisions for the 2018 Edition for Business Occupant Load Factors as well as definitions of net and gross floor areas (Table 1004.1.2 and Chapter 2 Definitions, respectively).
Lastly, occupant loads of 50 people or more in a single space would still consider the space to be assembly and not a business occupancy. Large presentation rooms, training areas, or lecture halls can quickly introduce assembly occupancy requirements that are unaffected by these changes.
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Roughly 160 years ago the development of the industrial revolution brought together people and production into a far greater density than had ever been experienced in history. What was once individual merchants and small productions gave way to the centralized factory. With it came new and larger fire hazards not realized before.
Early Manual Systems
Early attempts at suppression for fires in these environments (other than manual intervention by responders) included manual piped systems, which fed water to different zones of a building and ended with permeated pipes. These crude systems still required intervention to activate, only provided water after fire had grown, and had issues with plug-holing due to rust or debris in the pipe network.
The next iterations involved coating the pipe with tar that melted in a fire, opening holes in pipe that allowed water to arrive near where it was needed. The delivery of water in the manual system was still delayed, and a remaining issue remained concerning water distribution.
Parmelee's Automatic Sprinkler
Cue the automatic fire sprinkler, the first modern version of which Henry S. Parmelee famously developed in 1878. The new sprinkler featured a solder-sealed cap between water-filled pipe and a perforated shell, which could more precisely relate to temperature.
The initial sprinkler still delayed in activation as the soldered element was subject to conduction with cool water from the system and a thermal lag from the brass shell. This was improved upon by Frederick Grinnell, who incorporated a soldered element which was not subject to pressures from the water, was exposed to the temperature of the room (removing the thermal lag), and had a a toothed deflector that better distributed water.
Early fire sprinklers often had small deflectors, allowing uprights to direct more spray at ceilings which were often combustible. Over half a century later with manufacturing developments and continued innovation, storage application sprinklers like the Control Mode and then Early Suppression Fast Response were brought to market.
What interests me about the early development was that we were somewhat destined to end up with fire sprinklers constructed in the way we do now. The fire sprinkler is a reliable mechanical device with far greater precision and reliability than nearly all of the public seems to know. It operates independently, simply, and reliably.
Despite so many years between the original sprinklers and now, the principles and basic premises are very nearly what was dreamed about by early innovators. I wonder if in those early years they had any concept of the impact or number of lives those basic devices would save.
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We prefer wet-pipe sprinkler systems over dry-pipe systems for a handful of reasons: lower cost, no pipe slope requirements, potentially less points of drainage, can locate inspection & testing at the riser, less maintenance, testing and inspection requirements, no power needs, less noisy, and much less potential for corrosion.
However, when dry systems are needed, there's several issues to consider for the end-user.
For owners who are not associated with the intricacies of design and maintenance of dry systems, the most frequent compliant we hear about is with the noise associated with the dry system air compressors.
Dry-pipe systems are fed with pressurized air by a compressor. The compressor run-time frequency and duration is directly attributed to the amount of leakage in the system. Some people directly attribute the leakage of the system to the quality of installation due to the final tightness of fittings.
Air injected into a leaky system develops two problems. The first is increased potential for corrosion as fresh air naturally contains water moisture and oxygen, the two ingredients for corrosion. Air that feels comfortable to us offers sufficient products to encourage corrosion, and leaky systems tend to fail with corrosive issues much earlier in their lifetime.
The second issue is noise. While it sounds trivial, noise isn't for the employee whose cubicle is next to the riser room.
If leaky systems cause issues, why don't contractors prevent or fix leaky systems?
Fixing Leaky Systems
Once a system is installed and pressure tested to meet minimum standards, finding points of leakage is very tedious and time consuming. Just finding a few leaky fittings requires inspecting every joint and adjusting connection points. Needless to say, if a system isn't installed with tight fittings it becomes a very time-intensive and costly proposition to fix.
Lessening Leakage and Noise in Design
As a designer I naturally have less impact on the quality of installation than I do of the design, and there are several ways to help lessen the impact of leakage and noise.
Leakage requirements could be mandated to be leak less than prescribed code minimums. I've found this route doesn't exactly make good friends of contractors.
Noise can be reduced in a number of ways. First is to use tank-mounted air compressors in lieu of riser-mounted air compressors. Tanks act as a pressurized reserve, where they can reduce the frequency which compressors run in order to supply the system. Mounting to the tank also vibrates the tank, and not the piping network that runs through a building. Vibration on the pipe network requires absorption by the building, which contributes to higher ambient noise. The base of the tank can be isolated with vibration isolation (often rubber pads), again helping to reduce vibration transmission to the building. The downside to tank-mounted compressors is an increased cost and needs for additional floor space.
Another important consideration is where the compressor is located. Often the allotted space for risers are determined architecturally, but upfront coordination and planning to help prevent locating dry riser rooms next to normally occupied spaces can have major benefits. If the dry riser room must be near occupied spaces, consider requesting insulation within walls or acoustic panels to help absorb sound.
Quiet-Series Air Compressors
Lastly, one of my favorite products to hit the market in the last couple years offers a major solution to the noise issue. I'll start by saying I don't have any family or friends that work for General Air Products. They have not reached out to me to offer any money (although if you're out there General Air I'd be happy to share an address for a check). That disclaimer aside I really love the Q-Series (Quiet Series) General Air Compressors for fire sprinkler systems.
The Q-Series air compressor model can be tank-mounted and is significantly quieter than standard air compressors. The noise for the Q-Series have reduced noise by 20 dBA from the previous 80 dBA of standard oil-less compressors. For drywalled, carpeted rooms the effective sound from the Q-Series compressor is only slightly higher than ambient noise levels of a typical office.
The video above (by General Air) shows the difference in compressor noise. Needless to say it would be great for applications in hospitals, schools, offices, hotels, retail, nursing homes, and other areas sensitive to noise. We've found these to be a great solution to a common and intrusive issue of noise with dry risers near occupied spaces.
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If you haven't felt that tinge of anxiousness in the air, then you probably aren't spending time near someone taking the 2017 PE Exam.
This Friday over 200 professionals throughout the world will sit for the eight-hour Fire Protection P.E. Exam. It's a recognized mark of competency and for those taking the exam, a major milestone in his or her career.
In May of this year we published the 2017 MeyerFire PE Prep Guide, which introduced over 100 new questions, additional tips and references, and major revisions to the 2016 Guide. It was nothing short of a monstrous effort to compile the new 376-page volume. In addition, in June we launched a 20-week Weekly Exam Series in an effort to provide more practice while simulating actual exam conditions. This was joined by our continued free Daily PE Problems throughout the summer.
While this year was a big step up in involvement, it also was a very positive experience. We have had probably our most involved group of test takers to date, both in the number of questions posed, comments on the daily problems, and lively discussions in the PE Prep Facebook Group. A handful of last year's examinees provided real-time feedback in the Facebook discussions and a couple helped us compile new daily problems for this year.
There have been some learning curves on my end that cropped up this summer - namely needing better editing on my part as we had (in my opinion) too many errata updates to the 376-page guide. We will be incorporating all of those updates in the 2018 Guide. Another improvement I'm wanting for 2018 is to open up my availability late in the fall (September & October) better one-on-one help. I'll be exploring ways to better share and discuss content between now and next summer in that regard.
This summer I have again been impressed by how hard and thorough so many test takers are in their preparation. We've had some of the most in-depth content discussions around prep material of any summer to date. It seems as though the more problems and content we're able to distribute, the more discussion and depth everyone is able to soak up. It's certainly a good thing from a learning perspective.
For those taking the exam this week, remember that each year there's always some subject that appears completely out of nowhere. Just remember that those are just as surprising to everyone else taking the exam, and, some of those questions may not even be scored but rather trial questions for future exams. Do your best and forget the rest.
For those not taking the exam but know someone that is, give him or her a hug. Or don't, because that creeps people out - but do encourage beforehand and help celebrate with them afterwards. It's a big effort and for many an anxious time, but can be just as rewarding as well.
Showcase your job opportunity to our active community of fire protection professionals (designers, engineers, inspectors, review authorities, and more).
Our emails are read over 3,000 times monthly, and our site regularly brings over 35,000 page views each month (38,485 in August and 40,693 in September), all reaching professionals in the fire protection industry. This offers a great opportunity to reach a tremendous audience with your job opportunity.
We're excited about this new outlet where we hope to serve both job hunters and suppliers. As a launch offer, the first 15 subscribers who checkout using coupon code JOBS2017 will get a free listing. Post your job opportunity and find more information here.
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I grabbed something different this week and revisited the classic Fahrenheit 451 by Ray Bradbury. If you have not read the short fiction, it is centered around Guy Montag, a fireman in the near future who ignites rather than fight fires.
His dystopian world is governed by invasive mass media and a real fear for independent ideas and thought. People have little time or regard for each other or any thirst for knowledge, rather preferring information that are “digest of digests”, compoundings of simple summaries so vanilla and basic as to not offend any for feeling unintelligent.
While we don’t live in the exact environment Bradbury describes, there are parallels to our current day. Ever passed someone with a cell phone that wouldn’t recognize your existence? Ever get the impression like mass media is invasive, or a source of constant noise?
Fire in the novel is the tool by which this dystopian society denounces and discredits individual thought, effectively censoring anything that could be considered contrary to public needs. The title gets its name from the autoignition temperature of a book (although we know now that books self-ignite at ranges of temperatures which are dependent upon the materials).
Besides using fire as a theme throughout the novel to describe the pains of censorship, I find the biggest parallel to our industry is concept of individual knowledge growth. Knowledge or true independent thought cannot be gained simply by asking "how". Rather, it can be far more important to ask "why?".
We live by standards. In fire protection, especially in the United States, we are constantly in the realm of prescriptive code requirements whose rules we commit to memory and treat in high regard.
But why are those rules in place? It is not enough to simply know how plans are arranged, systems are installed, or how inspections are conducted. Our value as an expert is all about understanding the why, or the importance and implications behind the rules.
What is the good of experience if you've never stopped to ask why?
I have experienced several times in group or teaching environments where where learners want to know the how but not the why. How to lay out sprinklers with a given obstruction? How to layout fire alarm appliances for a movie theater?
How to orient branch piping for a dry system in a parking garage?
As a teacher it can be easy to deliver the how and provide a solution. But how much is lost in the opportunity to learn and teach in that moment? We fail our understudies if we don't provide ample reasoning as to why decisions are made or solutions are suggested. Our goal is to develop knowledgeable thought leaders, not machines that duplicate past work.
As a learner it can be all too easy and tempting to find short term solutions without digging deeper. In the design and construction industries, time can be our most valuable asset which does not lend itself to long duration of self study.
In order to make our experience translate to wisdom, we must ask why.
Good engineering judgement, often related to experience (but not necessarily a guarantee from it) is built upon a constant thirst for learning and growth. That thirst may be what brought you here.
I won’t even pretend to say that I’ve captured the why behind such a deep and varied engineering discipline like fire protection. It will be many years and many challenges before I will begin to scrape the surface of understanding much of the why behind our profession.
But I will make the most of that journey by asking why.
"I always wondered why somebody doesn't do something about that. Then I realized I was somebody." - Lily Tomlin
Wouldn't it be convenient to know about free online training from around the industry, without having to constantly check dozens of websites to keep on top of it all? As part of our effort to connect those in and around the fire protection community, we've started a Tools & Resources page which includes upcoming free webinars and other training events.
If you subscribe to our Weekly Blog or Daily posts, you'll start to see listings at the bottom of your regular emails. If you haven't subscribed, you can do so here.
Have a webinar you'd like to share with us? Contact us for more information about getting it posted on our site.
What you do is important.
I was again reminded of the critical nature of fire protection planning, prevention, and response when reading Nat Brandt's 2003 book "Chicago Death Trap: The Iroquois Theatre Fire of 1903." It was and still is the largest loss of life in U.S. History due solely to a fire.
Touted proudly as "Absolutely Fireproof," the Iroquois Theatre opened as destination of grand opulence and ornate design. On December 30th, just over a month after opening, a calcium arclight on stage shorted, causing roughly 6-inches of wire to overheat and ignite. A nearby drop curtain quickly caught fire, spreading the flames up through the vast amounts of scenery material above the stage.
Attempts to extinguish the fire using chemical canisters were ineffective, and an asbestos fire curtain failed to lower into place due to lighting supports that obstructed the curtain's path. In an attempt to thwart the electrical nature of the early fire, stage lights were shut off, but broken fuses then left the auditorium and lobby without any light. Covered, confusing, unmarked exits and some with locked doors made egress in the auditorium and through the lobby impossible for many, resulting in a rushed panic, trampling, and further blocking of exits.
Within five minutes of ignition nearly the entire set above the stage was inflamed. A large iron door to the rear of the stage was opened by stagehands escaping the fire, only giving fresh air to the fire. Skylights above the stage, which had intended to open as smoke and heat vents, were inoperable due to clamps not removed after installation. Exhaust above the rear of the auditorium pulled smoke up and into the auditorium.
Within a half hour the fire was completely extinguished, with a death toll due to trampling and smoke inhalation that still is unfathomable.
Contributors to Loss of Life
Early attribution to the 602 deaths from the fire was incorrectly blamed upon panic, in part a chauvinist attitude that the crowd full of women and children acted inappropriately. Later study and report identified numerous major contributors to the major loss of life as
It was mentioned that given our modern understanding for fire hazard and egress, it was surprising that most of the 1700 people in attendance that day were even able to escape.
Following the fire, tougher inspections began throughout the country and in theaters worldwide. All theatres in Chicago were closed until inspected for safety could be completed.
After years of legal disputes, ultimately no one was found legally responsible for the tragedy. Reform brought clearer language to ordinances with better enforcing authority, but even those were slow to change. Major changes as a result of the fire included:
Thoughts on The Book by Nat Brandt
This powerful volume was well comprised and focus almost entirely on the fire and its aftermath with long-standing implications. I would recommend it for those who want to understand the awful implications of very poorly planned construction paired with lack of enforcement.
As a father, this was a very difficult read. There were stories of efforts to escape the fire by so many (successful and unsuccessful), but particularly awful was the large numbers of women and children who couldn't escape. I cannot imagine the incredible toll this event had for victim's families. It is truly sad that such a long list of fallacies were overlooked to create such a horrendous tragedy.
Do we have the problem solved today? Do all areas of the world have resources to prevent these kinds of tragedies? I wish the answer was yes. What I can say is that I feel fortunate to live in a time and location where there is more recognition and enforcement for life safety, and to be in a position to help contribute towards a safer built environment.
Protecting life is important. What you contribute as part of the fire protection industry is important.
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You're already familiar with the inspector's test as a required component of a sprinkler system, but today we're diving into the true purpose and details behind this important aspect of a sprinkler system.
The purpose of the Inspector's Test can include: providing the ability to (1) test the sprinkler system's alarm/waterflow device, (2) test the opening of a dry-pipe or pre-action valve (for dry-pipe or pre-action systems systems, of course), (3) test the trip time from when the valve is opened to the arrival of water, where necessary, and (4) can aid in venting trapped air.
The inspector's test can be coupled as an air vent for a wet system or an auxiliary drain, although we'll explore those components in more detail separately.
Discharge: Used to discharge water during the test or draining of the system. Discharge must:
Drum Drip: Provided for dry or pre-action systems to collect condensate within the system for purging. At a minimum they must be:
Orifice: The orifice (within a sight/site glass) simulates the flow of a single sprinkler in order to ensure that the sprinkler waterflow alarm will activate upon the flow of a single sprinkler. The orifice must:
Sight/Site Glass: typically provided where water discharge is not visible from the control valve (NFPA 13 2002 A.18.104.22.168, 2007-13 A.22.214.171.124, 2016 A.126.96.36.199). As a side note, I don't understand why Drive Thrus and Site Glasses are spelled the way they are, but I don't try to fight the system. Just know that common language often refers to these as 'site' glasses despite not actually referring to a large area of land.
Supply: The supply simply connects the most remote branchline from the riser to the inspector's test (for a remote inspector's test). It must:
When & Where Required: inspector's tests are required on each wet, dry, or pre-action sprinkler system:
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I’ve rethought my career only a few times in my life. None of which were very serious, often more or less originating as daydreams of becoming a full time artist and living on a beach. Not so a few years into the profession when I ran into a major design issue on a premiere project.
The job was a large commercial headquarters split by a four-story atrium that was coming together as an architectural achievement in itself. Nothing outlandish or world-renowned, but in my limited experience it was the biggest and best project I had worked on to date.
Design phases came and went with big deadlines any consultant has surely experienced. Our scope at the time was limited to design-build (or performance specifications) fire alarm and sprinkler system plans and specifications. We coordinated standpipes, flow switches for smoke control zones, data center clean agent systems, graphic annunciators, and other features not commonplace in most office buildings.
It wasn’t until a day before my wife and I were to leave on a week-long Christmas vacation that I received word that a large change order coming based on a difference between our expectations for sprinkler protection and the contractor’s bid for both of the atrium’s four-story stairwells.
Today we're diving into the basic components of a fire sprinkler:
The orifice varies in size, but has a major impact on the sprinkler's k-factor which ultimately governs the sprinkler's relationship between flow and pressure. Opening sizes vary fairly dramatically but in general are not a major driver for sprinkler selection.
The nominal threading sizes range in quarter-inch increments from 1/2-inch to 1-1/4-inch (although some dry pendent shafts do have 1-1/2-inch threads). Thread size of sprinklers can be gathered in the field simply by measuring the diameter of the thread shaft. Sprinklers with a k-factor greater than 5.6 are no longer allowed to have thread sizes of 1/2-inch (NFPA 13 2002-2016 Section 8.3.5).
The plug retains the water (and pressure) within the sprinkler and pipe network. Breakage of the liquid-filled glass bulb results in the release of the plug, and thereafter the water.
Sealed Liquid-Filled Glass Bulb
Modern commercial sprinklers mostly rely on the colored glass bulb as the thermal sensor in the fire sprinkler, but other types are still frequent as well. Color of the liquid within the bulb indicate the listed activation temperature of the sprinkler (and can be found in NFPA 13 2002-2016 Table 188.8.131.52).
Frame & Deflector
The frame can have many finishes, of which some of the more common are listed above. The deflector offers the basic premise of the fire sprinkler - which is to distribute water in a specific pattern to best combat a fire hazard within an enclosure. Deflectors vary depending upon the style of the sprinkler and work to achieve different objectives. A residential pendent, for example, throws water with greater emphasis to the walls and ceiling where hazards are more commonly present in residential occupancies.
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While smoke detectors often have recommended spacing of 30 feet (identified in manufacturer's product data), spacing 30-feet on center is not the only way to space smoke detectors. NFPA 72 offers two methods for spacing smoke detectors on smooth ceilings:
The first method is simply to provide detectors at their listed spacing (often 30 feet), center-to-center, and within half the distance (which is 15 feet) to walls. [NFPA 72 2002 184.108.40.206.3(A-B), 2007 220.127.116.11.3.1-.2, or 2010-2016 18.104.22.168.1(1)]
The second, often lesser-known method, is to provide smoke detectors such that all points on the ceiling are within a distance of 0.7 times the listed spacing, or less [NFPA 72 2002 Section 22.214.171.124.3(E), 2007 126.96.36.199.3.5, or 2010-2016 188.8.131.52.1(2)].
Applying the Method
In practice, this simply results in drawing a 21 foot circle (0.7 x 30-foot spacing = 21 feet) around each detector and making sure that every point on the ceiling is covered. On site, it would simply result in making sure every spot on the ceiling is within 21 feet of a smoke detector.
This second method becomes important for complex room configurations, long and narrow corridors, or as a way to simply provide smoke detectors at their most efficient coverage.
A corridor which is 100-feet long and 10-feet wide, for instance, would require 4 smoke detectors under their listed spacing (30-feet spacing on center and 15-feet to the corridor ends). Using the second spacing method allowed by NFPA 72, these smoke detectors can be spaced nearly 41 feet center-to-center, requiring only 3 smoke detectors to be used.
Using the Second Method
Fundamentally, the theory is that smoke production will fill a ceiling based on the area of the ceiling. For a long, narrow corridor, smoke will be limited in it's spread in the narrow dimension, forcing travel down the corridor. As a result, smoke detector response time is dependent upon the amount of area the detector covers, not necessarily the spacing between detectors.
Matching smoke detector layouts to the nature of smoke transport and this code allowance could result in a simpler approach and often the need for less smoke detectors overall.
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We are very excited to announce that we are launching new platform for Daily Discussion!
Starting Monday of next week, we will anonymously post open ended-questions that you submit. The technical questions will be distributed to our active community just as the PE Problems are now, and anyone willing to share their expertise will be invited to partake in the discussion. Our hope is that over time we provide opportunities for experts around the country and around the world to weigh in on and learn from the active discussions surrounding the daily questions.
We've kicked around various forms of the concept ever since we debuted the daily PE Problems a few years ago, but the interest and feedback gathered since we started has encouraged us to find ways to bring new content and better engage with the sharp, engaging audience that we hear from regularly.
Ready to submit a question? They can be anything in fire protection, from fire alarm to sprinkler, life safety to passive fire protection, theory to application. All questions are published anonymously:
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