# Presentation: 940701

## Louise C. Speitel
Fire Safety Branch
FAA William J. Hughes Technical Center
Atlantic City International Airport, NJ  08405  USA

Louise.Speitel@faa.gov

- Fire Safety Branch
- FAA William J. Hughes Technical Center
- Atlantic City International Airport, NJ  08405  USA
- Louise.Speitel@faa.gov

**Handheld Extinguisher Draft Advisory Circular Summary**

- Aircraft Systems Fire Protection Working Group Meeting
-   Atlantic City, New Jersey
- October 25 - 26, 2006

## OUTLINE OF TALK

-   Background
-   Purpose of the handheld advisory circular (AC)
-   FAR requirements for hand-held extinguishers
-   Minimum performance standard (MPS) for transport category aircraft
-   Fire fighting guidance
-   Toxicity: decomposition products, agent, low oxygen hypoxia
-   Safe use of hand extinguishers
-  Ventilated and unventilated compatments
-  Accessible Cargo Compartments in Passenger/Cargo & Cargo Aircraft
-   AC language for halocarbon fire extinguishers

## BACKGROUND 

-  The Montreal Protocol and U.S. Clean Air Act requires phase out of ozone depleting halons and transition to available alternatives.
-  Halon replacement hand extinguishers are available meeting UL and MPS requirements and FAA safe-use guidelines:
-  HCFC Blend B
-  HFC-236fa
-  HFC-227ea.
-  A draft halon replacement hand extinguisher advisory circular has been submitted to The FAA Aircraft Certification Office.
-  A FAA Technical Report “Halocarbon Handheld Extinguisher Handbook” will include safe use guidance for agents introduced after the publication of this Advisory Circular.** **
-  Shortages of Halon 1211 expected within the next few years
-  Current A/C 20-42C for halons will be revised later.

## PURPOSE OF ADVISORY CIRCULAR

-   Provide safety guidance for halon replacement agents.
-  Effectiveness in fighting onboard fires.
-  Toxicity
-  Provides updated general information.
-   Applies to aircraft and rotorcraft.
-   Refers to outside documents:
-  ASTM specifications
-  MPS for hand fire extinguisher for transport category aircraft** **
-  Federal Aviation Regulations (FARS)
-  CFR Title 40: Protection of the Environment, Part 82- Protection of Stratospheric Ozone, Subpart G, Significant New Alternatives Program and Subpart H- Halon Emissions Program.
-  FAA Policy Letter

**PURPOSE OF ADVISORY CIRCULAR**

##   Specifies the minimum number of Halon 1211 or equivalent extinguishers for various size aircraft. 

-   Specifies the minimum number of Halon 1211 or equivalent extinguishers for various size aircraft.
-   Specifies the location and distribution of extinguishers on an aircraft.
-   Each extinguisher must be approved.
-   Each extinguisher intended for use in a personnel compartment must be designed to minimize the hazard of toxic gas concentration.
-   The type and quantity of extinguishing agent, if other than Halon 1211, must be appropriate for the kinds of fires likely to occur.
-   The FAR does not give extinguisher ratings. This is done in the AC.

## THE MINIMUM PERFORMANCE STANDARD  (MPS) 

**FOR HAND-HELD EXTINGUISHERS**

-   Provides specifications for equivalency to required Halon 1211 5 B:C extinguishers to satisfy FARS citing “Halon 1211 or equivalent”:
-   UL rated 5 B:C Halocarbon extinguishers that will be replacing required 2 1⁄2 lb. Halon 1211 lb extinguishers in transport category aircraft must pass 2 tests identified in DOT/FAA/AR-01/37 _Development of a Minimum Performance Standard (MPS) for Hand-Held Fire Extinguishers as a Replacement for Halon 1211 on Civilian Transport Category Aircraft_.
-   Hidden Fire Test
-   Seat Fire/Toxic_i_ty Test (for decomposition products of the agent). Guidance for agent toxicity can be found in the advisory circular.

## FAA POLICY LETTER

-   UL listed 5B:C and equivalent EN3 listed hand extinguishers replacing required 21⁄2 lb. extinguishers must meet the MPS for hand extinguishers.
-  Hidden Fire Test
-  Seat Fire/Toxic_i_ty Test** **
-   A permanent label must be affixed to the extinguisher :
-  Label identifies FAA approval for UL listed 5B:C extinguishers for use onboard transport category aircraft based on meeting the MPS test requirements.

## EXTINGUISHER LISTINGS FOR HALON REPACEMENT HALOCARBONS

**Aircraft Cabin:**** **
-   Recommends a minimum 5B:C UL or equivalent  listing.
-   Always provide the recommended number of hand held extinguishers with the proper UL rating, even in spaces where the toxicity guidelines are exceeded.** **
**  **If the safe-use guidelines are exceeded, select the safest extinguisher of the required UL listing and use only the amount necessary to extinguish the fire.
- Halon replacement extinguishers with a minimum rating of 5B:C can be used in place of required TSO’d water extinguishers if it can be shown that the replacement extinguisher has comparable or better class A extinguishing performance than the TSO’d water extinguisher.** **
-  Two required TSOd water extinguishers in close proximity may be replaced by one halon replacement extinguisher if the extinguisher has been shown to have comparable or better class A fire extinguishing capability as both water extinguishers.** **

## DRAFT ADVISORY CIRCULAR

**Accessible Cargo Compartments: Passenger/Cargo & Cargo Aircraft:**
-   Recommends a minimum extinguisher listing  of 2A:10B:C for compartments less than 200 ft3
-   Compartments 200 ft3 and larger should meet the requirements of the FAA Airworthiness Directive  AD 93-07-15. This AD provides options to the use of hand extinguishers:
-  Conversion to meet Class C cargo compartment requirements
-  Use fire containment containers or covers.

## ACCESSIBLE CARGO COMPARTMENTS

**Cabin Safety Guidance:**
-  Cargo extinguishers should be available to fight cabin fires
-  Select a cargo extinguisher that meets the safe use guidance for the aircraft cabin.
-  If no cargo extinguisher meets the safe use guidance for the aircraft cabin:
-  Consider installing a class C fire flooding suppression system in the cargo compartment or alternatives to handheld extinguishers that would provide effective fire protection.
-  Use the required UL listed extinguisher.
-  Select the least toxic agent of the required UL listing. Place a placard alongside the bottle stating: “Discharge of the entire contents of this size bottle into the occupied cabin area exceeds safe exposure limits. Use only the amount necessary to extinguish a fire”

## THROW RANGE

-   The MPS requires  a minimum throw range of 6-8 feet
-    A longer throw range of 10 feet or greater provides significant advantages in fighting fires in large aircraft cabins
-    A shorter throw range with a  lower velocity discharge is less likely to cause splashing &/ or splattering of the burning material. Consider a shorter throw range for very small aircraft
-   Select a range that would allow the firefighter to effectively fight fires likely to occur.

## FIXED NOZZLE/HOSE/ ADJUSTABLE WAND

-   For access to underseat, overhead and difficult to reach locations, it is recommended that extinguishers be equipped with a discharge hose or adjustable wand.
-   An extinguisher with a discharge hose or adjustable wand is more likely to result in the extinguisher being properly held during use.
-   Provides a means of directing a stream of agent to more inaccessible areas.
-   Fixed nozzle and adjustable wand allows one-handed use.

## TOXICITY CONSIDERATIONS

** ****Toxicity of the halocarbon itself**
-  Cardiotoxicity
-  Anesthetic Effects
-  Guidelines in the proposed circular are stricter than UL 2129 “Halocarbon Clean Agent Fire Extinguishers”. Immediate egress is assumed in the UL 2129 standard.
**  ****Low oxygen hypoxia: Very small aircraft**
**  ****Toxicity of halocarbon** **decomposition products**
** **Guidelines set in the Minimum Performance Standard for Handheld Extinguishers

## SAFE-USE GUIDANCE 

-    Use science-based safe-use approach published in peer-reviewed literature.
-   Conservative
-   More accurate than approach used for halons** **
-   The safe-use guidance is based on an assessment of the relationship between halocarbons in the blood and any adverse toxicological or physiological effect.
-   Separate guidance provided to avoid low oxygen hypoxia.
-   Includes guidance for general aviation as well as transport category aircraft.
-  ** **Operators of non-transport category aircraft should become familiar with the information in this AC
** **

## SAFE-USE GUIDANCE

**  ****Safe human exposure limits,**** up to 5 minutes are derived using a Physiologically-based Pharmacokinetic (PBPK) modeling of measured agent levels in blood . **
**  ****Assume 70F (21.1C) cabin temperature, perfect mixing, and the maximum cirtificated cabin P altitudes:**
**  ****8,000 ft-  Pressurized Aircraft .**
** ****12,500 ft- ****Nonpressurized aircraft with no supplemental oxygen.**
** ****14,000 ft- ****Nonpressurized aircraft**** with no supplemental oxygen.**
** ****18,000 ft- ****Nonpressurized aircraft**** with nasal cannula oxygen supply.**
** ****25,000 ft- ****Nonpressurized aircraft**** with oxygen masks (diluter demand).**
**  ****Non-ventilated aircraft: **
** ****The allowed concentration would be based on the 5-minute PBPK safe human concentration if available. Otherwise,  the “No Observable Adverse Effect Level” (NOAEL) may be used. **
** ****Table provides maximum safe weight/volume ratios for the aircraft cabin.**
**  ****Ventilated aircraft:**** Selector graphs  will be included if PBPK data is available for that agent. **

## AGENT TOXICITY :

**MAXIMUM SAFE CONCENTRATIONS**

- Total agent available from all extinguishers should not be capable (assuming perfect mixing) of producing concentrations in the compartment by volume, at _**70oF (21.1oC)**__ __**when discharged at altitude**_   (for the appropriate pressure altitude), that exceeds the agent’s safe exposure guidelines. *(Note: Designing for altitude provides a large safety factor for ground use. No need for 120**o**F correction)*
**  ****Nonventilated passenger or crew compartments:**
- PBPK derived 5 minute safe human exposure concentration, if known.
- If PBPK data is not available, the agent No Observable Adverse Effect Level **(NOAEL)**  is to be used. *(Note: UL 2129 allows use of a (sometimes higher) LOAEL Concentration)*
**  ****Ventilated Compartments:**
-  Use ventilation selector graphs to obtain the maximum agent weight per unit volume allowed in the cabin. Graphs are based on PBPK modeling of theoretical concentration decay curves & perfect mixing. If graphs are not available, follow concentration guidelines for nonventilated compartments.

## Solve equation or use  table:

- S = Specific volume of the agent at sea level:
-          At  70oF (21.1oC):  S= _____ ft3/lb
- A = Altitude correction factor for S:
-           8000 ft:       A= 760/ 564.59 = 1.346
-         12,500 ft:      A= 760/ 474.09 = 1.603
-        14,000 ft:       A= 760/ 446.63 = 1.702
-        18,000 ft:       A= 760/ 397.77 = 1.911
-        25,000 ft:       A= 760/ 282.40 = 2.691
-  CAltitude is the maximum safe clean agent concentration (%)
-  *C**Altitude ** is not altitude dependent.*

***Solve equation or use  table:***

**MAXIMUM SAFE WEIGHT OF AGENT WITH                     NO VENTILATION**

- (W/V)Safe is based on ***all***** **hand extinguishers in the compartment
- (The cabin is a compartment)

## AGENT TOXICITY: MINIMUM SAFE COMPARTMENT WEIGHT/VOLUME    (NO VENTILATION, 70oF, 21.1oC) 

**Total agent from all extinguishers in compartment, released at 70****oF****: (21.1oC)**

| Agent | Minimum Safe W/V (pounds/ft3) 1,2,3 |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- |
|  | Sea Level
(For info only) | 8,000 ft P Altitude
(Pressurized Cabin) | 12,500 ft Cabin P Altitude | 14,000 ft   Cabin
P Altitude | 18,000 ft Cabin P Altitude Nasal Cannula Oxygen Supply | 25,000 ft Cabin P Altitude
Diluter-Demand Oxygen Mask |
| HCFC Blend B | 0.00389 | 0.00289 | 0.00245 | 0.00229 | 0.00195 | 0.00145 |
| HFC-236fa | 0.0579 | 0.0432 | 0.0365 | 0.0342 | 0.0292 | 0.0216 |
| HFC-227ea | 0.0532 | 0.0394 | 0.0335 | 0.0313 | 0.0266 | 0.0197 |
| Halon 12114 | 0.00450 | 0.0034 | 0.00284 | 0.00264 | 0.00225 | 0.00167 |

***Use this table if air change time is unknown, or exceeds 6 minutes.***
***Multiply W/V by the compartment volume to get the maximum safe weight.***
***Divide total agent  weight from all ext. in compartment by W/V to get the min. safe volume.  Safety improves as min. safe volume decreases for extinguishers of same ul rating.***
***If the proposed halocarbon extinguisher AC was applied to Halon 1211.***
***Table footnotes  provide W/V multiplication factors if egress analysis is preformed and approved and escape time < 30 seconds.  Data not available yet for HCFC Blend B.***

## Appendix

**MINIMUM SAFE COMPARTMENT VOLUME    ****(NO VENTILATION, 70oF, 21.1****oC****) **

- For the following 5 B:C extinguishers, released at 70oF: (21.1oC)

| Agent       | Agent Weight1 (lbs) | Minimum Safe Volume (ft3) 2, 3 |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- |
|  |  | Sea Level
(For info only) | 8,000 ft P Altitude
(Pressurized Cabin) | 14,000 ft   P Altitude cabin | 18,000 ft 4 P Altitude Cabin Nasal Cannula Oxygen Supply | 25,000 P altitude cabin
Diluter-Demand Oxygen Mask |
| HCFC Blend B | 5.2 | 1337 | 1799 | 2276 | 2533 | 3586 |
| HFC-236fa | 4.75 | 85 | 115 | 145 | 163 | 220 |
| HFC-227ea | 5.75 | 108 | 146 | 184 | 2161 | 292 |
| Halon 12115
 | 2.5 | 556 | 749 | 947 | 1111 | 1497 |

***The agent weight fo a 5 B:C extinguisher is extinguisher dependent.***
***Use this table if air change time is unknown or exceeds 6 minutes***
***Multiply this number by the number of extinguishers in the aircraft***
***If nasal cannula oxygen on-board***
***(If the proposed halocarbon extinguisher AC was applied to the Halons)***

***nasal cannula***

*Appendix*

## AGENT TOXICITY: MINIMUM SAFE COMPARTMENT WEIGHT/VOLUME    (NO VENTILATION, 70oF, 21.1oC) 

**Total agent from all extinguishers in compartment, released at 70****oF****: (21.1oC)**

***Use this table if air change time is unknown, or exceeds 6 minutes.***
***Multiply W/V by the compartment volume to get the maximum safe weight.***
***Divide total agent  weight from all ext. in compartment by W/V to get the min. safe volume.  Safety improves as min. safe volume decreases for a given number of extinguishers of same UL rating.***
***If the proposed halocarbon extinguisher AC was applied to Halon 1211.***
***W/V multiplication factors if egress analysis is preformed and approved and escape time < 30 seconds.  MF******HFC236fa30sec******=  15/12.5 = 1.20                                                             ******	******	******	******           MF******HFC227ea30sec******=  12/10.5 = 1.14***
***PBPK data is not available yet for HCFC Blend B.  PBPK data is needed to determine multiplication factor.***

## Appendix

**(NO VENTILATION, 8000 FT ALTITUDE, ****70oF****)**

| Aircraft/ Helicopter | Vol (ft3) | Max No. Seats | Halon 1211 |  |  | HFC-236fa | Halotron 1 | HFC-227ea |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
|  |  |  | AC20-42C & UL1093 | AC20-42C
1 air-change /min | New AC | New AC | New AC | New AC |
| Cessna 152- | 77 | 2 | 0.3 | 0.4 | 0.1 | 0.6 | 0.04 | 0.5 |
| Cessna 210C | 140 | 6 | 0.5 | 0.7 | 0.2 | 1.2 | 0.08 | 1.0 |
| Cessna C421B | 217 | 10 | 0.7 | 1.1 | 0.3 | 1.9 | 0.1 | 1.5 |
| Sikorsky S76 | 204 | 14 | 0.7 | ___ | 0.2 | 1.8 | 0.1 | 1.4 |
| B727-100 | 5,333 | 131 | 17 | ___ | 6.4 | 47 | 3.1 | 37 |
| B767-200 | 11,265 | 255 | 36 | ___ | 14 | 98 | 6.5 | 77 |
| B 747 | 27,899 | 500 | 90 | ___ | 34 | 243 | 16 | 192 |

|  | Less than one 5 B:C extinguisher allowed |
| --- | --- |

*Appendix*

## VENTILATION

-    ***WARNING***:  Small increase in concentration above the Maximum Safe 5 Minute Exposure Concentration results in a much shorter  time to effect:
- Safe human exposure to constant concentration:
- HFC 236fa : 12.5% for 5 min, 15% for 30 sec.
- HFC 227ea: 10.5% for 5 min, 12.0% for 30 sec.,
-   Development of  Ventilation Tables:
-   Based on total weight of agent for ***all*** extinguishers in compartment.
-   Stratification of agents is a realistic expectation. It can be a safety benefit or disbenefit. Perfect mixing is assumed.
-   Agent manufacturers apply pharmacokinetic modeling  of blood concentration data to perfect mixing agent decay concentration curves.
-  Selector graphs for ventilated aircraft can be developed from that data.
-  Selector graphs provide the maximum agent weight per unit cabin volume allowed in a compartment for any known air change time.

## (assuming perfect mixing)

##   = Air Change Time

**Ventilated Cabin**
** ******** ****= Air Change Time**
**where:  C(t) = C****0**** ****.   ****Exp(-t/********)**
**Solution:**

## KINETIC MODELING OF ARTERIAL HALON 1211 BLOOD CONCENTRATION IN VENTILATED AIRCRAFT

**Critical Arterial Concentration**

**The peak arterial concentrations are used to develop the selector curves**

****** ****=1 minute**

****** ****=6 minutes**

****** ****= Air Change Time **

**Critical Arterial Concentration**

## KINETIC MODELING OF ARTERIAL HFC236fa BLOOD CONCENTRATION IN VENTILATED AIRCRAFT

**KINETIC MODELING OF ARTERIAL ****HFC236fa**** BLOOD CONCENTRATION IN VENTILATED AIRCRAFT**

**The peak arterial concentrations are used to develop the selector curves**

*k**1**= 27.73*
*k**2**= 3.924*

****** ****= Air Change Time**

## KINETIC MODELING OF ARTERIAL HFC237ea BLOOD CONCENTRATION IN VENTILATED AIRCRAFT

**The peak arterial concentrations are used to develop the selector curves**

****** ****= Air Change Time**

****** ****=6 minutes**

**Critical Arterial Concentration**

****** ****=0.5 minute**

****** ****=6 minutes**

*k**1**= 13.0*
*k**2**= 5.36*

## HFC-236fa SELECTOR FOR

** ****VENTILATED COMPARTMENTS**

***Perfect mixing assumed***

**Selector curves are avalable for:**
**HFC-236fa**** and ****HFC-227ea ****at:**
**8,000 ft**
**12,500 ft**
**14,000 ft**
**18,000 ft**
**25,000 ft pressure altitudes**

## HFC236fa SELECTOR FOR

** ****VENTILATED COMPARTMENTS**

***Perfect mixing assumed***

**  ****If the air change time is unknown, or exceeds 6 minutes, do not exceed the maximum safe HFC-236fa W/V ratio for unventilated aircraft: W/V= 0.0361 pounds/ft****3 ****for unpressurized cabins at 12,500 ft. Pressure Altitude.**
***  ******The total weight of agent for all extinguishers in the aircraft cabin is the basis for these maximum safe weight/volume ratios.***
**  ****Ventilate **_**immediately**_**, preferably overboard after successfully extinguishing the fire. Increase ventilation to the highest possible rate, and turn off any air recirculation systems, if equipped.**
***  ******All Unpressurized aircraft should descend immediately at the maximum safe rate to an altitude that is as low as practicable.***
***  ******Unpressurized aircraft equipped to fly above 12,500 feet should also follow additional precautions in 8.3.2 to prevent the hazards of low oxygen hypoxia (oxygen masks or nasal cannula as applicable).***** **

## HFC236fa SELECTOR FOR

** ****VENTILATED COMPARTMENTS**

***Perfect mixing assumed***

- Ventilate immediately after fire extinguished. Increase ventilation to the highest possible rate.
- If Air change time is unknown or exceeds 6 minutes, use unventilated data (Prolonged exposure to these agents may be hazardous):
-  W/V = 0.0432 pounds/ft3 for Pressurized Cabins at 8,000 ft. P altitude
-  W/V = 0.0361 pounds/ft3 for Nonpressurized Cabins at 12,500 ft.
-  W/V = 0.0342** **pounds/ft3 for Nonpressurized Cabins at 14,000 ft.
-  W/V = 0.0292 pounds/ft3 for Nonpressurized Cabins at 18,000 ft.
-  W/V = 0.0216 pounds/ft3 for Nonpressurized Cabins at** **25,000 ft.
- Unpressurized aircraft should descend at* *the maximum safe rate to the minimum practicable altitude to avoid the life threatening hazards of hypoxia resulting from the agent displacing oxygen from the air and to minimize exposure to halogenated agents. This guidance should be followed regardless of ventilation rate.

## 1st ORDER KINETIC MODELING OF ARTERIAL 

**BLOOD CONCENTRATION HISTORIES**

-   Provides a ***simple mathematical solution***  to obtain data needed to develop perfect mixing ventilation tables which will provide maximum safe extinguishing agent weights for a range of compartment volumes and air change times.
-   Monte Carlo simulations of arterial blood concentration histories for 5 minute exposures to constant agent concentrations are used as input data for developing equations (95% confidence) for each extinguishing agent.
-   PBPK arterial blood data has been published for HFC 236fa and HFC 227fa which accounts for 95% (two standard deviations) of the simulated population having 5 minute arterial  blood concentrations below the target concentration.
-   Equations can be developed for each agent, which transform agent concentration histories to arterial blood concentration histories in ventilated spaces.
-   Demonstrated to work for predicting blood concentration histories for exposures to a constant concentration of agent.
-   Has been validated for predicting blood concentration histories for exposures to changing concentrations of agent.

## LOW OXYGEN HYPOXIA AT ALTITUDE: 

**Unpressurized Small Aircraft**

##  Provide safety guidance for halocarbon extinguishers.

-  Provide safety guidance for halocarbon extinguishers.
-  Recommends a minimum UL listed 5 B:C extinguisher for occupied spaces
-  The proposed A/C references requirements for hand extinguishers.
-  Recommends throw ranges for various sized aircraft
-  Recommends a discharge hose or adjustable wand.
-  Provides guidance for minimizing risk of low oxygen hypoxia when agent is released at altitude.
-  States the maximum weight that ***all*** extinguishers in a compartment should not exceed, based on agent toxicity, size of compartment, and maximum FAA-allowed altitude of the cabin.

##   May allow increased halocarbon clean agent concentrations in ventilated compartments: 

-   May allow increased** **halocarbon clean agent concentrations in ventilated compartments:
-  Selector graphs can be developed if PBPK data is available.
-  Selector graphs provide the maximum safe weight of agent based on safe concentration at altitude, compartment volume, time for an air change.
-  Provides updated safe handling guidelines based on adverse toxicological or cardiac sensitization events, PBPK modeling, and hypoxia considerations.
-  Operators of non-transport category aircraft should become familiar with the information in this A/C.
-    The proposed AC is subject to change/ rewrite by the FAA Aircraft Certification Office.

## WORKING GROUP PARTICIPANTS

** ****Louise Speitel****	****	****FAA**
** ****Doug Ferguson****	****	****Boeing**
** ****Kendall Krieg****	****	****Boeing**
** ****Rich Mazzone****	****	****Boeing**
** ****Bradford Colton****	****	****American Pacific Corp **
** ****Howard Hammel****	****	****Dupont**
** ****Steve Happenny    ****	****	****FAA**
** ****Paul Hinderliter****	****	****Dupont, Haskell Labs**
** ****Gary Jepson****	****	****Dupont, Haskell Labs**
** ****Bella Maranion****	****	****EPA**
** ****Reva Rubenstein****	****	****ICF Consulting**
** ****Robert Shaffstall****	****	****FAA, Civil Aeromedical Institute      **
** ****Arnold Angelici****	****	****FAA, Civil Aeromedical Institute**
** ****Al Thornton****	****	****Great Lakes Chemical Co.**
** ****Mike Miller ****	****	****Kidde Aerospace**
** ****Mark Bathie****	****	****CASA, Australia**

## http://www.fire.tc.faa.gov

- _[http://www.fire.tc.faa.gov](http://www.fire.tc.faa.gov/)_