### Risk Analysis for CO 2 

### , HFC - 152a, and Hydrocarbon Refrigerants in MACs

Erin Birgfeld, U.S. EPA Earth Technologies Forum April 23, 2003

### Risk Assessment of Alternative MAC

Systems

• Identify and characterize risk

• Identify risk mitigation strategies

• Provide reliable information for industry and government

### EPA MAC Risk Analysis Team

• Erin Birgfeld, MPH, Risk Analysis

• Dave Godwin, P.E., Engineering

• Stephen Andersen, Ph.D.

### Government/Industry Partnership

• U.S. EPA

• Australian Greenhouse Office

• DENSO

• Toyota

• DaimlerChrysler

• Japan METI and EA • Fiat

• Underwriters Laboratories

• U.S. Army, CECOM

• Delphi

• General Motors Industry participation and expertise critical for a successful project

### Current Status: Where are we now?

• Request industry to provide any existing data or risk analysis information to EPA

• Consult with industry and gov’t representatives

• Summarize and consolidate information

• Plan a strategy and draft risk assessment

### Convene Meeting(s) of Government and

Industry Experts

• Review technical information and inputs to risk assessment

– Assure all reasonable aspects are considered

• Gain insights into national and regional perspectives

• Define additional research that may be needed

### Outcome

• Risk assessment report published by year end

– Issued jointly by gov’t and industry

• Significant New Alternatives Policy (SNAP) Program to review and act on promising alternatives

• Industry decisions on new systems

### Risk Assessment Overview

• Compare likely exposure to levels where a hazard exists

• SNAP sponsored a fault tree analysis (FTA) for 134a and other non - flammable refrigerants

– Estimates frequency of occupational and passenger exposures to refrigerants

– Performed to assess toxicity issues

### Fault Tree Analysis (Jetter, 2001)

• Definitions

### Conclusions of FTA by Jetter et al.

• Most exposures are within acceptable limits

• Engineering can mitigate exposure

– Reducing Charge Size

– Reconfiguring cooling system

– Increasing airflow/intake

### Next Generation Alternatives

• CO 2

– High pressure systems

– Low toxicity but causes narcotic and other effects at higher concentrations
• HFC 152a

– Toxicity is low and well characterized (similar to 134a, R - 12)

– Flammability concerns
• Hydrocarbons (Propane, Isobutane)

– Low toxicity

– Flammability concerns

### Proposed Strategy for Risk Analysis

• Refine FTA to address high pressure CO 2 systems and system using flammable refrigerants

– passengers and technicians

• Identify safe upper bound exposure levels for short and long term exposures to CO 2 (Ongoing)

– Medical literature: NASA/Navy research

– Consider sensitive groups

### Proposed Strategy for Risk Analysis (con’t)

• Computerized Fluid Dynamic Modeling (CFD) conducted by Dr. Neal Blackwell, Army CECOM

– Work funded through AAPPSO

• Assess magnitude of flammability and CO 2 hazards without expensive testing

– Quality inputs/assumptions critical

– Industry input necessary

### Conclusion and Next Steps

• Goal is to provide a comprehensive unbiased risk assessment for alternative systems

• Further input from industry and other interested parties on risk assessment strategy

• Draft risk assessment paper by July 15, SAE’s Alternate Refrigerant Symposium

## Contacts

• Erin Birgfeld (202) 564 - 9079 birgfeld.erin@epa.gov • Dave Godwin (202) 564 - 3517 godwin.dave@epa.gov