Questions & Answers

  • UL 300 is a:
    • Code
    • NFPA Standard
    • Law
    • Fire test standard for manufacturers of pre-engineered system.

  • D

UL 300 is a fire test procedure written by UL to ensure that all manufacturers are performing the same tests, in the same manner, in order to list their products with ULI.

  • What was the primary reason for the new UL 300 standard?
    • More revenue for UL, manufacturers, and distributors.
    • Improve appliance protection.
    • Improve duct and plenum protection.

  • B

The change in UL 300 were specific to the appliances in an effort to provide test protocols that more closely reflect real world fire risks. 

  • When was the effective date for UL 300?

  • November 21, 1994

The original effective date was January 13, 1194, but was delayed because of changes made to the standard.

  • What appliances were affected by UL 300 test protocol changes?

  • Fryers, griddles, ranges, charbroilers (gas radiant, electric, lava rock), woks, upright broilers, charcoal, or mesquite.


  • The real world fire hazards accounted for in UL 300 were the use of newer "high efficiency" appliances, detector reaction time prior to fuel shut-off, and the use of vegetable shortening rather than animal fat. True or False?


  • True

The three major changes recently in fire testing were:

- The use of commercially available appliances that met specific heat up and cool down rates.

- The use of vegetable shortening with more severe burning characteristics (auto-ignition temperatures of 685 F or higher).

- Leaving the appliance heat source on during a two-minute pre-burn time instead of tuning the appliance off prior to a one-minute pre-burn.

Items A & C were the most critical changes.

  • On average, how much more wet agent is required to protect fryers against the UL 300 fire test protocol?
    • 3 times more
    • 5 times more
    • 7 times more

  • B

Although each manufacturer's system is different, on average five times more agent is required for protection of fryers. Changes discussed in question 5 result in a more intense fire that is difficult to extinguish and far more difficult to secure against reflash.

  • What UL 300 test protocol change were made to improve fryer protection?
    • Test appliance was changed from fabricated pan (to simulate a fryer) to commercial gas fryer with specific heating and cooling rates.
    • One minute pre-burn after auto-ignition was changed to two minute pre-burn.
    • Appliance fuel-off condition during pre-burn was changed to appliance fuel-on condition.
    • Minimum grease auto-ignition temp of 685 F was added.
    • All of the above.

  • E

The combination of all of these changes presents a much more difficult fire test, which in turn leads to a greater safety margin in real world applications.

  • UL 300 requires splash tests for which appliances?
    • Fryers
    • Range tops
    • Griddles
    • Woks

  • A, B, D

Both extinguishments splash tests (no burning grease ejected from appliance during extinguishments) and cooking temperature splash tests (no grease droplets larger than 3/16 inch splashed from the appliance). Note: Failure of a splash test constitutes failure of the system at that nozzle location, even if fire extinguishments have been achieved.

  • As long as I have new pre-UL 300 cylinder assemblies, I can continue to install those systems in accordance with the old installation manual referenced on the cylinder True or False?

  • True and False

According to UL, system manufactured before November 21, 1994 can be installed after November 21, 1994. However, several state fire marshals and  other local authorities have issued mandatory compliance deadlines. Check with your AHJ to ensure compliance. Additionally, some manufacturers have issued statements regarding time limits for such installations. Check with manufacturer before installing.

  • Existing systems remain acceptable as long as the system is:
    • Installed in its original location.
    • Protecting original equipment, without any changes.
    • In compliance with its original listing.

  • A

UL's requirement provide the basis for UL to conduct follow-up service inspections at the time of manufacturer. However, it is the AHJ, not UL that governs the acceptability of installation. Some manufacturers will not accept liability for pre-UL 300 systems that have been salvaged and re-installed in another location. This action is far beyond the concept of "grandfathering"..

  • Under what conditions may installed pre-UL 300 systems be removed and reinstalled at different locations?
    • When it is a wet agent system.
    • When it is reinstalled to meet the current UL 300 standard.
    • When acceptable to the authority having jurisdiction.
    • Under no circumstances.

  • C

When acceptable to authorities having jurisdiction.

  • An existing cylinder assembly manufactured before November 21, 1994, and installed in a pre-UL 300 system develops a leak. The manufacturer replaces the cylinder assembly under warranty with a cylinder assembly accompanying with the new UL 300. Upgrading of the system is not required.

  • False

UL has stated that anywhere a new UL 300 cylinder assembly bearing the UL mask is used, that system must comply with the referenced installation manual. Replacement cylinder assemblies may be provided without the UL mark on the label; however, this may affect the acceptability of the system to the authority having jurisdiction.

  • There is no way to know whether a cylinder assembly is listed in accordance with UL 300 other than to look at the cylinder assembly manufacturing date.

  • False

Cylinder label references the manufacturer's installation, operation, maintenance, and recharge manual , thus linking the cylinder assembly and system design to the listed limits. In some cases, the label may also state "meets the requirements of Standard UL 300".

  • When an installed pre-UL 300 systems required to be replaced or upgraded?
    • When the protected appliance is a deep fat fryer without dual limit switches.
    • When fryers are protected with dry chemicalsystems.
    • When AHJ or the insurance company mandates replacement/upgrade.
    • All of the above.

  • C

The requirement for replacement or upgrading of pre-UL 300 system units may come from the authority having jurisdiction or the insurance company involved. UL does not require replacement or upgrading of old systems.

  • When upgrading an existing system, you must add a label to the cylinder stating that the system is installed in compliance with the appropriate installation manual.

  • False

Although there is no UL requirement for the additional label, most manufacturers are making such a label available.

  • There are no UL listed pre-engineered dry chemical systems that comply with the current UL 300. True or False?

  • True

UL has confirmed that no UL 300 listings currently exist for dry chemical system units intended to protect restaurant cooking areas. Testing by manufacturers has shown that while dry chemical systems can extinguish the UL 300 fire tests, reflash is likely to occur due to the lack of cooling. 

  • When my customer adds a new appliance to an old system, I need to upgrade the entire system using equipment complying with the new UL 300.

  • True and False

The addition of another appliance to a pre-UL 300 system would not require that the entire system be upgraded to the new standard if coverable with the existing cylinder(s) under the parameters of the existing installation manual. If new cylinder assemblies manufactured after November 21, 1994 are added, then the system may need to be upgraded. Check with your AHJ since installation requirements may vary.

  • When upgrading an existing dry chemical systems using equipment complying with the new UL 300, the duct and plenum coverage must also be converted to wet agent protection. True or False?

  • False

If the duct is protected by a separate dry chemical system, then only appliance protection need be upgraded to meet the new requirements, unless otherwise mandated by the AHJ. However, both wet and dry systems must discharge simultaneously  and be listed by the manufacturer specifically for that operation.

  • If a fire occurs in the cooking appliance or hood and duct, which of these provide the best line of defense?
    • The manual pull.
    • The fuse link actuated automatic system.
    • A portable fire extinguisher.

  • A

The heat responsive link may take one minute or more to react and is intended as an automatic means to actuate the system if human intervention is not possible. The manual pull is a fastest means to react to the fire and should always be used before a portable extinguisher, because actuation of the system also shuts off power or gas to the appliance. Of course, the fire department should also be called and the building evacuated. 

  • If I use 500 F degree links in every system, I will be safe because the system will actuate eventually.

  • False

Manufacturers provide recommendations for choosing the proper fuse links. These recommendations should be followed. In general, the most rapid acting link not likely to cause an unwanted discharge should be used.

  • I can feel confident about servicing systems without checking the fuel shut-offs as long as I know that they are in place. . True or False?

  • False

The correct operation of fuel shut-off devices is critical to successful fire suppression of cooking appliance hazards even for UL 300 listed systems..

  • Isn't it unrealistic to consider the system to be the prime means of extinguishment and the hand portable secondary backup when the system discharge will rewire shutdown and more clean-up?

  • No

Realistically, the most efficient fire suppression will occur when the manual pull of the system is activated. Actuating the system will turn off the heat sources to the appliances and apply agent efficiently without improper human appliance techniques. If appliance heat sources are not turned off, multiple extinguishers can be used and reflash may still occur. Down-time and clean-up may be greater after discharging several extinguishers and then having the system discharge. Certainly any chance of increasing damage by leaving the appliance heat source on while attempting extinguishment with hand portables will also affect down-time.

  • UL listed 4OB:C and 8OB:C extinguishers have been tested, listed, and designed specifically for commercial cooking grease fires. True or False?

  • False

UL tests for B rated extinguishers use n-heptane in-depth fires to assign ratings. No commercial cooking appliances or shortenings are used for B rated extinguishers. No commercial cooking appliances or shortenings are used for B rated extinguishers. A new classification for fire extinguishers for use in commercial cooking area (Class K) has been proposed for inclusion in NFPA 10, and UL has developed a corresponding draft fire testing protocol that does use a commercial cooking appliance and commercial shortening. When NFPA 10 is revised to include Class K extinguishers, manufacturers will list portable extinguishers specifically for this use.

  • Since dry chemical extinguishing systems manufactured after November 21, 1994 and intended for the protection of restaurant cooking areas are not currently authorized to bear the UL Listing Mark, portable dry chemical fire extinguishers are not to be used on commercial cooking grease fires. True or False?

  • False

NFPA 10 currently specifies the use of sodium bicarbonate and potassium bicarbonate dry chemical fire extinguishers for the protection of cooking grease fires. A recent TIA submitted by FEMA has been approved NFPA Standards Council. The TIA incorporated wet chemical portable extinguishers into NFPA 10 as acceptable protection. Dry chemical extinguishers with appropriate ratings remain acceptable.

  • The UL 300 test specifies the use of gas fryers and vegetable shortening because the tests proved that these are worst case. True or False?

  • True


  • The real world fire hazards accounted for in UL 300 were the newer high effeciency appliances and the use of vegetable shortening rather than animal fat.

  • True

The two major changes recently in restaurants include: 1. high energy efficiency appliances to reduce costs, which are better insulated and retain heat that increases the difficulty of extinguishment; & 2. the use of low cholesterol vegetable shortening which has more severe burning characteristics (auto-ignition temperature of 685 F or greater).


  • If the protected fryer is electric and/or uses animal fat, it is safe to assume that pre-UL 300 systems will provide acceptable protection. True or False?

  • False

Since pre-UL 300 fryer fire tests were not conducted with electric fryers and/or animal fat, there isnot data to support this assumption. Therefore, all fryers must have the same protection regardless of fryer heat source or type of shortening used.

  • Pre-UL listed systems without automatic fuel shut downs must be upgraded to UL 300 protection standards, including shut downs. True or False?

  • No Answer

The question, not the answer, is false. There is no such thing as a pre-UL 300 listed system without shut downs. All UL listed restaurant fire protection systems - before and after UL 300 - must include automatic shut downs. Without automatic shut downs, there is virtually no chance a fryer will not reflash after initial extinguishment regardless of the level of dry or wet chemical protection.

  • Older fryers without overheat shut-off devices (high limit switches) are more likely to cause runaway fire than newer fryers with mandatory overheat shut off devices. True or False?

  • True


  • If I have two 28" by 24" griddles sitting side by side, I can protect them with a UL 300 listed system that has griddle coverage of 28" by 50" with one nozzle. True or False?

  • False

Part of UL 300 testing requires that each appliance must be covered individually unless  a specific listing in the manufacturer's design, installation, and maintenance manual. In order to obtain a listing covering multiple appliances with a single nozzle, the manufacturer must specifically test this arrangement under the UL 300 test standard.

  • When I see special fryer listings in some manuals that refer to a specific fryer brand name and model number, can I use this coverage for all fryers and retain the UL 300 listings?

  • No

This is called an "Appliance Specific" listing and such coverage is only UL listed with the make and model fryer that is referenced in the manual. "Flat Bottom" or "Specialty" fryers often do not meet UL 300 requirements for grease depth, heat-up rate, and /or cool down rates for fryers used in testing.

In order to obtain a listing for a "Flat Bottom" or "Specialty" fryer, UL ties the coverage to the specific make and model appliance that was tested. This type of coverage is not to be used on other deep fat fryers.

  • What are some obvious signs for an AHJ or maintenance technician to look for in determining that a system is not UL 300 listed?
    • System uses dry chemical coverage on appliances.
    • System uses a single nozzle to protect multiple appliances.
    • System has only one agent cylinder.
    • System was manufactured before November 21, 1994.
    • System protects a combination griddle/range with one nozzle.

  • A, B, E

To Date, no dry chemical system has been listed under UL 300; dry chemical may still be used for plenum and duct protection. Multiple Appliances must be treated individually under UL 300. A system using only one agent cylinder could still be within UL 300 limitations. A system manufactured before November 21, 1994 could have been installed within UL 300 listings, or could have been altered and upgraded to UL 300 listings. A combination griddle/range must be protected as two separate appliances or specifically listed in the manual under UL 300 testing.


  • Should dry chemical systems protecting appliances be replaced? True or False?

  • True & False

It is recommended that considerations be given to upgrading dry chemical systems protecting appliances to UL 300 systems. Any system without shut-offs is not listed and should be upgraded to a UL 300 system. Any system requiring alterations or that has had changes to the appliance (including the addition of high efficiency /high recovery fryers) should be upgraded to UL 300. An interpretation of "grandfathered" system indicates that pre-UL 300 systems, installed in accordance with their listing, are okay as long as no changes to the system or cooking equipment have been made. Pre-UL 300 systems that have had changes occur in the cooking equipment or require changes in the system should be replaced or upgraded toa UL 300 listed system.  

  • When updating existing dry chemical systems using equipment complying with the new UL 300, the duct and plenum coverage must also be converted to wet agent protection.

  • False

If the duct is protected by a separate dry chemical system, then only the appliance protection need be upgraded to meet the new requirements, unless otherwise mandated by the AHJ. However, both wet and dry systems must discharge simultaneously..

  • UL 300 compliance means:
    • All pre-engineered restaurant system units, including installed pre-UL 300 systems, must comply with UL 300 after the effective date.
    • All new pre-engineered restaurant system units installed on or after the effective date must be in compliance with UL 300.
    • All new pre-engineered restaurant system units manufactured on or after the effective date must be in compliance with UL 300.

  • C

UL audits the manufacturing of the product through the follow-up service at the factory..

  • If I install a system manufactured after November 21, 1994 using old nozzle coverage from a manual that was listed under UL Subject 300, is the installation in accordance with the UL listing? Yes or No?

  • No

Such an installation would not be in accordance with the UL listing since the design, installation, and maintenance manual is the part of that listing. AHJs, not UL, govern the acceptability of installations. However. most AHJ and local codes require systems listed by an independent testing laboratory. This installation would not be listed. Furthermore, since the manufacturer's design and installation instructions and requirements are being ignored, all liability for the system's performance will rest with the installing company.

  • There are no additional charges expected to UL 300.

  • False

Currently, several revisions to the published standard are being proposed to incorporate change made as a result of manufacturer's compliance testing. These revisions will not require additional testing by manufacturers currently in compliance. Further changes are possible through the UL standards development process to refine UL 300 further.


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Last modified: October, 2010