• No certification at this moment but it is under consideration
• Concerns about environmental benefits of D-F
• Options being considered:

• - R.49?
• - PMS (Portable emissions measurement system)
• - SEMS (Simplified emissions measurement system) (g/kg CO2)

• Challenges: determination of replacement ratio; measurement of CH4 (SEMS)
• Will there be enough D-F retrofit systems to motivate and create new rules?