ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 90

Revised Carbon Monoxide (CO) Standard for Class I and II
Nonhandheld New Nonroad Phase 1 Small Spark-Ignition Engines

ACTION:  Notice of proposed rulemaking.

SUMMARY:  Today EPA is proposing a revision of the Phase 1 carbon
monoxide (CO) emission standard for Class I and II new nonroad
spark-ignition (SI) engines at or below 19 kilowatts.  Today's
action would increase the standard from 469 grams per kilowatt-
hour (g/kW-hr) to 519 g/kW-hr.  This proposed action is necessary
to address the CO emission difference between oxygenated and
nonoxygenated fuels that was not reflected when the Agency
previously set the CO standard for these nonhandheld engines in a
final rule published July 3, 1995.  This correction of the
nonhandheld engine CO standard would ensure that the CO standard 
for manufacturers of Class I and II small SI engines used to
power equipment such as lawnmowers is achievable and otherwise
appropriate under the Clean Air Act and that it is technically
feasible for manufacturers to certify their engine models to the
Phase 1 emission standards and make them commercially available
for the 1997 model year.  

     In addition, today's action proposes to give the
Administrator the option to permit the use of open crankcases in
engines used exclusively to power snowthrowers.  This proposed
change will give EPA the flexibility to allow certain engine
manufacturers to certify engines to be used in snowthrowers
without making technological changes that would severely impair
the ability of the engine to function or that would be
economically prohibitive.    

FOR FURTHER INFORMATION CONTACT:  Laurel Horne, U.S.
Environmental Protection Agency, 2565 Plymouth Road, Ann Arbor,
MI 48105. Telephone:  (313) 741-7803.  FAX:  (313) 741-7816. 
Electronic mail:  horne.laurel@epamail.epa.gov

SUPPLEMENTARY INFORMATION:
I.  Regulated Entities.  Entities potentially regulated by this
action are those which manufacture engines used in nonhandheld
applications, such as lawnmowers, and those which manufacture
engines used exclusively to power snowthrowers.