1
 
                                  [LETTERHEAD]
 
                                November 7, 1994
 
Dear Fellow Puritan-Bennett Stockholder:
 
     On October 25, 1994, Thermo Electron Corporation commenced an unsolicited
tender offer to purchase all of the outstanding common stock of Puritan-Bennett
for $24.50 per share in cash.
 
     For the reasons set forth below and in the accompanying statement on
Schedule 14D-9, your Board of Directors has unanimously determined that the
Thermo Electron offer is not in the best interests of Puritan-Bennett and its
stockholders. YOUR BOARD STRONGLY RECOMMENDS THAT YOU REJECT THE OFFER AND NOT
TENDER YOUR SHARES TO THERMO ELECTRON.
 
     Your Board believes that Thermo Electron's offer seeks to deny you the full
value of your investment in Puritan-Bennett. Puritan-Bennett is early in the
process of implementing a carefully conceived long-term business plan after a
major restructuring during the past year, which put some major issues behind us.
Your Board fully expects an increasingly profitable future for Puritan-Bennett
to emerge from our outstanding technological and competitive positions. Thermo
Electron timed its offer to seize Puritan-Bennett's value before the market
fully appreciates the long-term benefits of the restructuring and other
initiatives we have undertaken. Puritan-Bennett is positioned to take advantage
of exciting growth opportunities, both in the United States and abroad,
especially in the home care respiratory products market, the fastest growing
part of our business, and also in the hospital and aviation markets. We want all
of our stockholders to reap these benefits, not just Thermo Electron. Thus,
after careful consideration, your Board has determined that it is in the best
interests of Puritan-Bennett and its stockholders that Puritan-Bennett remain
independent and continue to pursue its long-term business strategy.
 
     Before arriving at its recommendation, your Board carefully reviewed
Puritan-Bennett's businesses, financial condition, technologies and future
prospects, as well as the opinion of Smith Barney Inc. that the $24.50 per share
price provided for in the offer is grossly inadequate to Puritan-Bennett's
stockholders (other than Thermo Electron) from a financial point of view. The
Board also considered numerous other factors described in the attached Schedule
14D-9, including the recent FDA clearance of six new products and product
enhancements that offer the potential for additional revenues and strengthen our
competitive position in the critical care ventilator market and the fact that
Puritan-Bennett stock has traded as high as $35.50 per share as recently as
November 1992 and closed at $25.50 per share on November 4, 1994. Please read
carefully the attached Schedule 14D-9, which describes in depth your Board's
recommendation.
 
     Your Board firmly believes that the benefits of Puritan-Bennett's existing
projects and initiatives have not yet been fully reflected in the market -- and
that they certainly are not reflected in Thermo Electron's offer. In making its
offer at this time, Thermo Electron is trying to buy Puritan-Bennett at a
bargain price that does not reflect Puritan-Bennett's intrinsic value and the
long-term strategic promise that Thermo Electron itself has recognized.
 
     Thank you for your continued support and encouragement. Be assured that
your Board and management will continue to act in your best interests.
 
                                            Sincerely,
 
                                            Burton A. Dole, Jr.
                                            Chairman, President and
                                              Chief Executive Officer