The tractor-trailer struck the rear of the minivan with such force that all five passengers were propelled into the front seat area of the mangled smaller vehicle. Highly flammable fuel was leaking from the truck and the minivan as two of the van's passengers stopped breathing.

This was the scene that Ronald S. Pifer, an off-duty Fairfax County Fire and Rescue Department technician, came across while riding his motorcycle near Winchester last July. Using a tool supplied by another passing motorist, Pifer broke open a side window, entered the minivan and treated the crash victims until local fire and emergency medical crews arrived. Four of the injured people survived.

For his actions, Pifer will be awarded the Silver Medal of Valor, Fairfax County's highest honor for police, fire and rescue personnel, in a ceremony at noon Tuesday at the Hilton McLean Tysons Corner. Twenty others will also receive the medal during the 25th annual presentation of the Fairfax County Chamber of Commerce Valor Awards.

The master of ceremonies will be Emmy Award-winning journalist Bill Kurtis, host of A&E cable television network's "Investigative Reports" series.

A record 83 members of the county's Police Department, Sheriff's Office and Fire and Rescue Department will receive recognition from the chamber and the Board of Supervisors for various acts of heroism in the line of duty last year.

Other Silver Medal of Valor winners include Officer Melissa J. Jones for her efforts to stop an armed robbery of herself and of fellow off-duty officer Joseph N. Wallace, who will receive a Bronze Medal of Valor. Wallace was wounded by gunfire.

Officer Jonathan J. Bobel will receive the Silver Medal of Valor for rescuing three people from a fire-engulfed car after a traffic accident. Pfc. Katherine N. Luppino will receive the Bronze Medal for assisting at that scene.

Fire Lt. Wayne B. Stottlemyer will get a Silver Medal for the off-duty rescue of a 6-year-old girl who was trapped in an overturned SUV. Part of the vehicle collapsed on him.

Master Police Officer John D. Brocco and Pfc. Bradford S. Avery will receive the Silver Medal for their rescue efforts at the scene of another fiery automobile accident. Pfc. Kim A. Vanderveld will receive the Bronze Medal for his assistance at that same crash.

Fourteen members of the Sheriff's Office and the Police Department's undercover street crimes unit each will receive the Silver Medal for helping control a street riot during which a mob of about 60 gang members killed a bystander.

Those recipients are Lt. Timothy W. Hoover, 2nd Lt. Christopher Cochran, Sgt. Brian E. Hall, Master Police Officer Michael L. Twomey, and Police Officers 1st Class Ron Estrella, Donald J. Kline, Mark P. Dale, Edward K. Warren, Chad E. Mahoney, Steven L. Carroll, Donnacha G. Fay and Tom L. Hulse IV from the county police; and Sgt. Kevin Andariese and Pfc. Richard Mattison of the Sheriff's Office.

Other recipients of the Bronze Medal of Valor include Fire and Rescue Master Technician John C. Mayers and, in the Police Department, Sgt. James A. Cox; Lt. Tor J. Bennett; Pfcs. Michael P. Gibbons, Holly H. Hinkle, John T. Carney, John R. Debonis, Gregory P. Devine, Christopher T. Hayo, Eric P. Leeds and Richard M. Theal; 2nd Lt. Susan Lamar; Maj. Michael Lomonaco; and Officer Erica L. Slaight.

Lifesaving Awards will go to Fire and Rescue Department Technicians Gregory W. Hunter, David M. Gilmore, Bryan J. Nix and James H. Williams; Firefighter Juan C. Ayala; and Lt. Joseph Palau. In the Police Department, Lifesaving Awards will be given to Pfcs. Andrew J. Pytko, Jason E. Reichel, Richard M. Theal and Michael F. Grinnan; Lts. Erin F. Schaible and Amy E. Lubas; Assistant Supervisor Tammy L. Read; Supervisor Roy B. Shrout; Capt. John E. Hart; and Officer Walter R. Fasci. Public Safety Communicators Alicia D. Dale, Susan C. Farria, Lorraine C. Fells-Danzer and Judith C. Lassiter also will receive Lifesaving Awards.

And, in the Sheriff's Office, the following will receive Lifesaving Awards: Pfcs. Craig F. Carroll, Terry K. Hull, Irving T. Marshall, Jeffery W. Trullender, Sharon D. Fogle and Charles W. Taggart; Master Deputy Amy A. Gaisor; and Sgt. Kevin A. Timothy.

Certificates of Valor will be awarded to Deputy Randall S. Naeve and Pfcs. Leslie A. Sheehan, Michael A. Hammond and Dale R. Clark in the Sheriff's Office; Police Officers Michael A. Comer, Lee E. Redenbo and Matthew K. Kunstel; Police Sgt. Robin J. Davis; Master Police Officers John T. Flinn, Peter G. Masood and John D. Brocco; Police Pfcs. Steven G. Mihelarakis, John W. Hartle and Peter J. Kwak; retired Police Lt. Mark A. Rogers; Police 2nd Lt. Thomas L. Vaclavicek; and, in the Fire and Rescue Department, Senior Building Inspector Michael A. Andreano; and Firefighter James M. Furman.