<PAGE>
 
  The obligation of both Enterra and the Company to consummate the Energy
Industries Sale are conditioned upon: (a) receipt of all required regulatory
approvals, (b) no violation by the closing of the Energy Industries Sale of any
order of any court or other governmental authority, and (c) receipt of approval
of the Energy Industries Sale by the stockholders of the Company.

  Indemnification.  The Company has agreed to indemnify Enterra and its and its
affiliates after the Closing Date, from and against each claim paid, imposed or
incurred by such persons:  (a) resulting from any inaccuracy in any
representations or warranties of the Company under the Purchase Agreement or any
certificate delivered by the Company thereunder, (b) to the extent caused by a
breach of any covenant in the Purchase Agreement by the Company, (c) which is a
liability of the Company or Energy Industries other than an Assumed Liability,
(d) to the extent caused by any violation of any bulk sales law or other similar
state laws in respect of the transactions contemplated by the Purchase
Agreement, (e) with the exception of those matters governed by the following
clause (f), because of, resulting from or arising out of the business,
operations or assets of Energy Industries prior to the closing date (excluding
any Assumed Liabilities), or (f) to the extent caused by an environmental claim
or related liability which is caused by matters existing prior to the closing
date, subject to reduction to the extent the liability has been exacerbated by
Enterra after the closing date or to the extent Enterra failed to use reasonable
efforts to  mitigate such liability after the closing date, if Enterra actually
knew of such liability.  There is a $250,000 deductible, subject to exceptions
in certain cases, and a maximum aggregate liability of $4 million for claims
described in clauses (a), (b), (d), (e) and (f).

  Enterra has agreed to indemnify and hold harmless the Company and its
affiliates after the Closing Date from and against each claim paid, imposed on
or incurred by such persons: (a) resulting from any inaccuracy in any
representation or warranty of Enterra under the Purchase Agreement or any
agreement or certificate delivered by Enterra thereunder, (b) to the extent
caused by a breach of any covenant in the Purchase Agreement by Enterra, (c)
which is an Assumed Liability, or (d) because of, resulting from or arising out
of the operation of the natural gas compression business after the closing date.
There is a $250,000 deductible, subject to exceptions in certain cases, and a
maximum aggregate liability of $4 million for claims described in clauses (a),
(b) and (d).

  Non-Competition Covenant by the Company.  In connection with the Energy
Industries Sale, the Company agreed, and the Purchase Agreement so provides,
that, except for certain immaterial exceptions, for a period of three years
after the closing date, the Company will not manage, operate or control, or be
connected or a principal, agent, representative, consultant, investor, owner,
partner, manager or joint venturer with, any business or enterprise engaged in
any aspect of the natural gas compression business.

  Termination.  Even if the Energy Industries Sale Proposal is approved by the
Company's stockholders, the Purchase Agreement may be terminated by (a) mutual
written consent of the Company and Enterra; (b) by Enterra if any of the
conditions to Closing to be performed by the Company shall not have been
complied with or performed at the time required for such compliance or
performance; (c) by the Company if any of the conditions to Closing to be
performed by Enterra shall not have been complied with or performed at the time
required for such compliance or performance; (d) by Enterra or the Company if
the Closing Date shall not have occurred on or before December 20, 1995 or such
later date mutually agreed to by the parties; and (e) by Enterra or the Company
if any court or other governmental body shall have issued an order or taken any
other action prohibiting the transactions contemplated in the Purchase Agreement
which has become final and nonappealable.

  In the event that no transaction is consummated with Enterra, the Company may
seek opportunities to sell Energy Industries to another purchaser.  To date, no
significant negotiations have been conducted by the Company regarding the sale
of Energy Industries with persons other than Enterra.  However, the Company
expects the Energy Industries Sale to close pursuant to the terms of the
Purchase Agreement.

STOCKHOLDER APPROVAL

  Under Section 271 of the DGCL, stockholder approval is required for a Delaware
corporation to sell all or substantially all of its assets.  Because of the
uncertainty regarding the precise point at which asset sales will be deemed to
be substantially all of a company's assets, the Board of Directors of the
Company is seeking stockholder approval of the Energy Industries Sale so as to
remove any uncertainty that the transaction was properly authorized.

                                       9