# Presentation: 676662

## Handheld Advisory Circular Update

**Louise Speitel**
**Fire Safety Branch**
- FAA Wm. J. Hughes Technical Center
- Atlantic City International Airport, NJ  08405
**International Aircraft Systems Fire Protection Working Group **
- November 19-20, 2008
- Atlantic City, NJ   USA

## Dos and Don’ts

- FAA Aircraft Certification Service has advised the FAA Fire Safety Team that the Advisory Circular AC 20-42D is considered in the process of rulemaking.
- We cannot release a draft version or discuss the AC because ex parte communication of pending rulemaking is not permitted.
- We can discuss recent data on handheld agents that was not available when the task group was working on the draft AC.

## Outline

**   **_**Updated Data:**_
-   **Halon 1211:** Remove Max Safe W/V Selector Curves for Ventilated Compartments
-   **HCFC Blend B:** Add Max Safe W/V Data for Ventilated and Nonventilated Compartments
-   **Halocarbon Blends:** Provide Max Safe W/V Calculation Method.
**  **_**Methods**_**: **
**  **PBPK Modeling of HCFC-123 for Human Exposures to LOAEL Concentrations. Do not exceed Target Arterial Concentrations
-   Maximum Safe W/V Guidance for Blends

## PBPK Modeling Approach

_**LOAEL**_
- Lowest observable adverse effect level for a group of dogs exposed to a chemical **(%V/V)**
_**Standard FAA-accepted PBPK methodology:**_** **is described in
-     Allen Vinegar, Gary W. Jepson, Mark Cisneros, Reva Rubenstein, William J. Brock, “Setting Safe Acute Exposure Limits for Halon Replacement Chemicals using Physiologically Based Pharmocokinetic Modeling”, *InhalationToxicology. 12, pp. 751-763, 2000.*
_**Human PBPK Model**_
- Describes the uptake, distribution, metabolism, and elimination of inhaled halocarbons in the human body.
- This PBPK model includes a respiratory-tract region and a pulmonary exchange area
**Partition Coefficients: **

|  Liver |  Gut |
| --- | --- |
|  Fat  |  Slowly perfused tissues  |
|  Lung |  Rapidly perfused tissues |

## PBPK Modeling Approach (cont.)

_**Human PBPK Model (cont)**_
**Monte Carlo Method:**
- Monte Carlo simulations describe the effect of interindividual variability on the output of PBPK models : 2 standard deviations.
- Accounts for **97.5% **of the simulated population
**Target arterial Concentration:**
-  Out of a group of dogs exposed to each chemical at the LOAEL gas concentration, the lowest measured 5-min arterial concentration was taken as the target arterial concentration for use in modeling human exposure.
- Target arterial concentration: same for dogs and humans

## Halon 1211 PBPK-Based Maximum Safe W/V 

_**Halon 1211 PBPK Modeling Efforts don’t meet requirements:**_
- Al Vinegar’s  Halon1211 PBPK modeling articles:
-  Early work and a precurser to the more robust modeling efforts that followed.
- There is no measured dog arterial blood concentration at the NOAEL cardiac sensitization (CS) concentration.
- The human PBPK model was run at the LOAEL 1% gas concentration to simulate arterial blood concentrations to establish the “target” CS threshold blood level of Halon 1211.
- We can not locate references for the partition coefficients
- A Monte Carlo sort was not used: Clearly stated
_**Solution:**_
- Use NOAEL concentration in place of the maximum safe human exposure concentration to calculate the Maximum Safe W/V
- In the absence of an acceptable PBPK solution, one can not develop selector curves for the maximum safe W/V for ventilated aircraft compartments.

## HCFC-123 PBPK-Based Maximum Safe W/V 

_**Data presented for HCFC Blend B to obtain the target 5 minute concentration is in review.**_
_**HCFC-Blend B data not yet accepted by the FAA**_
_**Data is presented in following slides:**_

## PBPK Modeling of Halocarbons

**PBPK Modeling of Halocarbons**

## PBPK Modeling + 2SD of Constant Concentrations of HCFC-123

**PBPK Modeling + 2SD of Constant Concentrations of HCFC-123**

## PBPK Modeling of HCFC 123:Ventilated Compartments

**PBPK Modeling of HCFC 123:****Ventilated Compartments**

## PBPK Modeling Approach

**PBPK Modeling Approach**

## Maximum Safe Exposure Concentrations No Ventilation

| Agent  | NOAEL
(%v/v) | Max Safe 5 Minute Human Exposure
Concentration
(%v/v) | CSafe
(%v/v) |
| --- | --- | --- | --- |
| HCFC Blend B | 1.0 | 1.50 | 1.50 |
| HFC-227ea | 9.0 | 10.84 | 10.84 |
| HFC-236fa | 10.0 | 12.75 | 12.75 |
| Halon 1211 | 0.5 | N/A  | 0.5 |
| Halon 1301 | 5.0 | 6.25 | 6.25 |

## Maximum Safe W/V:  No Ventillation

| Agent | Maximum Safe W/V (lbs/ft3) |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- |
|  | Sea Level
(For info only) | Pressurized Aircraft
(8k ft. CPA) | Non-Pressurized Aircraft  |  |  |  |
|  |  |  | 12.5k ft.  | 14k ft.  | 18k ft.  |  25k ft.  |
| HCFC
Blend B  | 0.00586 | 0.00435 | 0.00367 | 0.00345 | 0.00294 | 0.00218 |
| HFC-227ea | 0.0551 | 0.0409 | 0.0344 | 0.0324 | 0.0275 | 0.0205 |
| HFC-236fa | 0.0595 | 0.0442 | 0.0371 | 0.0349 | 0.0297 | 0.0221 |
| Halon 1211 | 0.00224 | 0.00166 | 0.00139 | 0.00131 | 0.00112 | 0.000829 |
| Halon 1301 | 0.0260 | 0.0193 | 0.0162 | 0.0153 | 0.0130 | 0.00968 |

## Minimum Safe Compartment VolumesNo Ventilation

| 
Agent |   AgentWeight (lbs) | Minimum Safe Volume For One 5 B:C Extinguisher (ft3) |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- |
|  |  |      Sea Level (for info only) | Pressurized Aircraft | Non-Pressurized Aircraft |  |  |  |
|  |  |  | 8,000 ft          CPA | 12,500 ft | 14,000 ft        | 18,000 ft            | 25,000 ft                   |
| HCFC Blend B | 5.5 | 938 | 1264 | 1499 | 1593 | 1870 | 2525 |
| HFC-227ea | 5.5 | 99.8 | 135 | 160 | 170 | 200 | 269 |
| HFC-236fa | 4.75 | 79.8 | 107 | 128 | 136  | 159 | 214 |
| Halon 1211 | 2.5 | 1116 | 1502 | 1790 | 1908 | 2232 | 3016 |
| Halon 1301 | 5.0 | 192 | 258 | 308 | 327 | 385 | 517 |

## Number of 5 B:C Extinguishers That Can be Safely Installed at 8,000 ft CPA

*Unventilated*

| Aircraft | Volume
(ft3) | Max No.Seats | Halon 1211 |  | Halon 1301 | HCFC Blend B | HFC-236fa | HFC-227ea |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
|  |  |  | AC 20-42C andU.S. UL1093 | AC 20-42D | AC 20-42D | AC 20-42D | AC 20-42D | AC 20-42D |
| C 152 | 77 | 2 | 0.3 | 0.05 | 0.3 | 0.06 | 0.7 | 0.5 |
| C 210C | 140 | 6 | 0.5 | 0.09 | 0.5 | 0.1 | 1.3 | 1.0 |
| C 421B | 217 | 10 | 0.7 | 0.1 | 0.8 | 0.2 | 2.0 | 1.5 |
| S76 | 204 | 14 | 0.7 | 0.1 | 0.8 | 0.2 | 1.9 | 1.5 |
| CRJ200 | 2015 | 50 | 6.5 | 1.3 | 7.8 | 1.6 | 19 | 15 |
| B727-10 | 5,333 | 131 | 17 | 3.5 | 21 | 4.2 | 50 | 38 |
| B767-200 | 11,265 | 255 | 36 | 7.5 | 43 | 8.9 | 105 | 80 |
| B747 | 27,899 | 500 | 90 | 18 | 108 | 22 | 260 | 198 |

## Maximum Safe HCFC Blend B  W/V at 8,000 ft CPA

**Maximum Safe HCFC Blend B  W/V**** ****at 8,000 ft CPA**

## Maximum HCFC Blend B  W/V

## Halocarbon Blends

**    ****The maximum safe W/V for a blend can be calculated from the maximum safe W/V of halocarbon A and the maximum safe W/V of halocarbon B as follows:****	****	****	****	****	****	****	**

## ENVIRONMENTAL PROPERTIES

| Agent  | Formula | ODP  | GWP 
(100 years)  | Atmospheric Lifetime  (yrs)  |
| --- | --- | --- | --- | --- |
| Halon 1211  | CBrClF2  | 5.1  | 1300  | 11  |
| Halon 1301 | CBrF3 | 16 | 7140 | 65 |
| HCFC-123  | CHCl2CF3  | 0.012  | 120  | 1.4  |
| HFC-227ea  | CF3CHFCF3  | 0.0 | 3800  | 36.5  |
| HFC-236fa  | CF3CH2CF3  | 0.0 | 9400  | 226  |