EXHIBIT 10.4

GUARANTY SUPPLEMENT
To the Holders of the Series A Notes, (each, as
hereinafter defined) of STERIS Corporation
(the “Company”)

Ladies and Gentlemen:
    
WHEREAS, in order to obtain funds for the purposes set forth in Schedule 5.14 to
the
Note Purchase Agreement, the Company entered into that certain Note Purchase
Agreement
dated as of May 15, 2015 (the “Note Purchase Agreement”) between the Company and
each of the Holders as defined therein providing for, inter alia, the issue and
sale by the
Company of (a) $125,000,000 aggregate principal amount of its 3.45% Senior
Notes, Series
A-1, due May 14, 2025 (the “Series A-1 Notes”), (b) $125,000,000 aggregate
principal amount
of its 3.55% Senior Notes, Series A-2, due May 14, 2027 (the “Series A-2
Notes”), and (c)
$100,000,000 aggregate principal amount of its 3.70% Senior Notes, Series A-3,
due May
14, 2030 (the “Series A-3 Notes”; the Series A-1 Notes, the Series A-2 Notes and
the Series
A-3 Notes are hereinafter referred to as the “Series A Notes”). Each Holder of a
Note shall be
referred to as a “Holder”.

WHEREAS, as a condition precedent to the entering into the Note Purchase
Agreement
by the Holders, the Holders required that certain affiliates of the Company
enter into an
Affiliate Guaranty as security for the Notes (the “Guaranty”).

Pursuant to Section 9.7 of the Note Purchase Agreement, the Company has agreed
to
cause the undersigned, Synergy Health AST, LLC, a limited liability company
organized under the laws of Delaware, Synergy Health US Holdings, Inc., a
corporation organized under the laws of Delaware, and Synergy Health North
America, Inc., a corporation organized under the laws of Florida (the
“Additional Guarantors”), to join in the Guaranty. In accordance with the
requirements of the Guaranty, the Additional Guarantors desire to amend the
definition of Guarantor (as the same may have been heretofore amended) set forth
in the Guaranty attached hereto so that at all times from and after the date
hereof, the Additional Guarantors shall be jointly and severally liable as set
forth in the Guaranty for the obligations of the Company under the Note Purchase
Agreement and Notes to the extent and in the manner set forth in the Guaranty.

The undersigned is the duly elected President of each of the Additional
Guarantors, each a subsidiary of the Company, and is duly authorized to execute
and deliver this Guaranty Supplement to each of you. The execution by the
undersigned of this Guaranty Supplement shall evidence their consent to and
acknowledgment and approval of the terms set forth herein and in the Guaranty
and by such execution the Additional Guarantors shall be deemed to have made in
favor of the Holders the representations and warranties set forth in Section 5
of the Guaranty.

Upon execution of this Guaranty Supplement, the Guaranty shall be deemed to be

    

--------------------------------------------------------------------------------

amended as set forth above. Except as amended herein, the terms and provisions
of the Guaranty
are hereby ratified, confirmed and approved in all respects.

Any and all notices, requests, certificates and other instruments (including the
Notes) may refer to the Guaranty without making specific reference to this
Guaranty Supplement, but nevertheless all such references shall be deemed to
include this Guaranty Supplement unless the context shall otherwise require.
    

Dated: August 8, 2017

SYNERGY HEALTH AST, LLC

By:     /s/ Michael J. Tokich            

Name: Michael J. Tokich
Title: President

SYNERGY HEALTH US HOLDINGS, INC.

By:     /s/ Michael J. Tokich            

Name: Michael J. Tokich
Title: President

SYNERGY HEALTH NORTH AMERICA, INC.

By:     /s/ Michael J. Tokich            

Name: Michael J. Tokich
Title: President

ACCEPTED AND AGREED:

STERIS CORPORATION

By:     /s/ Michael J. Tokich            

Name: Michael J. Tokich
Title: Senior Vice President and Chief Financial Officer

[Signature Page to 2015 Guaranty Supplement - Joinder of Synergy Health]