Exhibit 10.6.4

FOURTH AMENDMENT TO LEASE

This Fourth Amendment to Lease (“Amendment”) is made and entered into this 18th
day of June, 2008, by and between Glenn Dale Business Center, L.L.C., a Maryland
limited liability company (“Landlord”), and TVI Corporation, a Maryland
corporation (“Tenant”).

W I T N E S S E T H:

WHEREAS, Landlord and Tenant are parties to a Lease dated February 16, 1998, as
amended by the First Amendment to Lease dated December 10, 2002, as amended by
the Second Amendment to Lease dated January 16, 2004, and as amended by the
Third Amendment to Lease dated March 29, 2004 (collectively the “Lease”),
whereby Tenant leases from Landlord certain premises containing approximately
one hundred eighteen thousand two hundred seventy-three (118,273) square feet,
known as Suites 200 and 200b (the “Premises”), located at 7100 Holladay Tyler
Road, Glenn Dale, Maryland (the “Building”) for a Term which expires on
April 30, 2010 (the “Current Term”); and

WHEREAS, Landlord and Tenant wish to amend the Lease by extending the Lease Term
by an additional five (5) years and to otherwise modify the Lease.

NOW THEREFORE, in consideration of the mutual covenants herein made, Landlord
and Tenant hereby enter into this Amendment and state as follows:

RECITALS. The foregoing recitals are incorporated herein by this reference.

CAPITALIZED TERMS. Unless otherwise defined herein, all capitalized terms shall
have the same meaning as they have been assigned in the Lease.

LEASE TERM. Notwithstanding any provision of the Lease to the contrary, the
Lease Term shall be extended by an additional five (5) years (the “Extension
Term”) following the expiration of the Current Term. The Extension Term shall
commence on May 1, 2010 (the “Extension Term Commencement Date”) and shall
expire on April 30, 2015 (the “Extension Term Expiration Date”). Notwithstanding
any provision of the Lease to the contrary, the Tenant shall have no right to
extend the Lease Term beyond April 30, 2015.

PREMISES. Tenant acknowledges that Tenant is currently in possession of the
Premises and, except as provided for in Paragraph 7 of this Amendment, Tenant
hereby accepts the Premises in its “as is” condition, subject, however, to
Landlord’s ongoing repair and maintenance obligations as required under the
Lease and the following corrective actions, all of which Tenant has notified
Landlord in writing:

 

  (i) Repair of roof leaks (The Landlord and Tenant acknowledge that the roof on
the Building has been replaced and is currently under warranty and thus, the
Landlord shall take commercially reasonable steps to enforce the roof warranty
in repairing any leaks); and

 

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  (ii) Fire Alarm System requires upgrades, repairs and/or replacements (The
Landlord and Tenant acknowledge that the Landlord is currently working on this
item.)

MINIMUM RENT. Tenant shall continue to pay Minimum Rent in the amounts and upon
the terms and conditions set forth in the Lease through February 28, 2009.
Beginning on March 1, 2009 and continuing throughout the Extension Term, Tenant
shall pay Minimum Rent in the amounts set forth in the following schedule:

 

Time Period

  

Per Square

Foot Rate

  

Annual Minimum

Rent

  

Monthly Minimum

Rent

3/1/09–2/28/10

   $5.53    $654,049.69    $54,504.14

3/1/10–4/30/11

   $5.81    $687,166.13    $57,263.84

5/1/11–4/30/12

   $6.10    $721,465.30    $60,122.11

5/1/12–4/30/13

   $6.25    $739,206.25    $61,600.52

5/1/13–4/30/14

   $6.41    $758,129.93    $63,177.49

5/1/14–4/30/15

   $6.57    $777,053.61    $64,754.47

ADDITIONAL RENT. For the remainder of the Current Term and throughout the
Extension Term, Tenant shall continue to pay its proportionate share of Real
Estate Taxes, Common Facilities Costs for the operation, maintenance and
management of the Common Facilities, and Insurance pursuant to the Lease. In
addition, Tenant shall continue to be responsible for the costs and expenses of
utilities, trash removal and janitorial services provided to the Premises and in
accordance with the Lease, as well as all other Additional Charges specified in
the Lease.

IMPROVEMENTS. (a) Promptly following the full execution of this Amendment,
Landlord shall, in a good and workmanlike manner, and in compliance with all
applicable laws, regulations, rules, orders, codes and ordinances, complete
improvements to a portion of the Premises containing approximately 30,000 square
feet (the “Renovated Premises”) in accordance with the following:

1) Tenant will cooperate with Landlord’s architect to promptly finalize the
working drawings and specifications of materials for the improvements that
Tenant desires beyond the “as is” condition of the Premises (the “Improvements”)
(which final working drawings will comply with the ADA, and will incorporate and
be consistent with the Building standards). The preliminary working drawings and
specifications will be completed and attached hereto and made a part hereof as
Exhibit A. Said drawings and specifications, when completed, will be ready to
submit for necessary permits. Such drawings and specifications must be approved
by Landlord prior to the commencement of any work related to the Improvements,
which approval shall not be unreasonably withheld, conditioned or delayed. As
modified by any Landlord reasonably-required changes, the final working drawings
will be the “Final Plans”. If Landlord fails to respond to Tenant within ten
(10) business days of request for approval, then Landlord shall be automatically
deemed to have approved the working drawings as the “Final Plans.” Tenant is
solely responsible for determining whether or not it is a public accommodation
and for compliance with ADA within the Premises. Landlord’s approval of the
plans, specifications and working drawings for Tenant’s alterations shall create
no responsibility or liability on the part of Landlord for their completeness,
design sufficiency, or compliance with all laws, rules and regulations of
governmental agencies or authorities.

 

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2) Landlord will be the construction manager for the construction of the
Improvements in accordance with the Final Plans. For the purpose of billing, the
cost of the Improvements will be Landlord’s cost of constructing the
Improvements, which includes a construction management fee of five percent
(5%) of the total design and construction costs for supervision and coordination
thereof. The cost of constructing the Improvements is estimated to be
$363,773.00 as set forth in the Project Budget set forth on Exhibit B attached
hereto and made a part hereof (the “Improvements Cost Estimate”). In the event
the cost of the Improvements exceeds the Improvement Cost Estimate, Landlord
agrees to notify Tenant in writing prior to performing the work and Tenant shall
have the right to approve in advance the cost overruns or modify the Final Plans
to reduce or eliminate the cost overruns. Landlord agrees that Tenant may use
Tenant’s contractor to erect the walls separating the Renovated Premises from
the remainder of the Premises.

3) Subject to Landlord’s obligations set forth in the Lease and in this
Amendment, Landlord’s obligations with respect to improvements and alterations
of the Premises shall be limited to the Improvements set forth in the Final
Plans.

(b) Landlord will provide Tenant with an allowance (the “Improvement Allowance”)
of up to $309,209.00 to be used for Improvements to the Premises. The
Improvement Allowance may be used to pay: (a) the construction management fee;
(b) the architectural and engineering fees, if any, relating to the Improvements
[including: (i) the architectural fees related to the preparation of all
drawings, (including CAD drawings) plans and specifications (collectively,
“plans”), and (ii) engineering fees related to the planning and performance of
the Improvements in the Premises]; and (c) all costs and expenses (including
permit fees) incurred in the construction of the Improvements, including,
without limitation, the purchase of air-conditioning units and related ductwork
and security device(s) at the entrance door to the Renovated Premises, over and
above the current “as is” condition of the Premises (collectively “Tenant’s
Costs”). Landlord will credit the Improvement Allowance against the foregoing
costs of constructing the Improvements. Tenant will pay as Additional Rent any
excess (the “Excess”) of Tenant’s Costs over the Improvement Allowance as
follows:

1) Upon approval of the Final Plans, Tenant shall pay to Landlord $54,564.00 of
the Excess.

2) Within thirty (30) days following the last to occur of (i) Substantial
Completion of the Improvements as evidenced by Landlord’s architect’s
certificate; (ii) receipt by Landlord of a certificate of occupancy (if
required); and (iii) submission to Tenant of the detailed final accounting for
all costs hereunder together with supporting documentation, Tenant shall pay to
Landlord any unpaid balance of the actual Excess based on the final costs if and
to the extent approved by Tenant in accordance with Paragraph 7(a)2.

 

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3) If the final costs for the Improvements are less than the Improvements Cost
Estimate, Landlord shall promptly credit to the next Rent payment, the
difference between the Improvements Cost Estimate and the final costs.

(c) Failure to make any such payments within thirty (30) days following delivery
of written notice to Tenant that same is due shall constitute a Default under
the Lease, entitling Landlord to all available remedies;

(d) If Tenant requires any changes in the approved drawings and specifications
for the Improvements (the “Tenant Changes”), Tenant must present Landlord with
revised drawings and specifications for Landlord’s approval, which approval
shall not be unreasonably withheld, conditioned or delayed. As a condition of
its approval, Landlord may require additional payments against the Excess, if
Landlord reasonably determines that the Tenant Changes will increase the Excess.
If Landlord approves the Tenant Changes, Landlord will incorporate such changes
in the Improvements.

(e) Substantial Completion shall be deemed to occur when the Improvements
specified herein have been completed in accordance with the Final Plans, except
for punch-list items which do not materially interfere with Tenant’s intended
use of the Premises.

(f) Tenant shall prepare and submit a punch-list to Landlord within ten
(10) business days of delivery to Tenant of notice of Substantial Completion via
email to svoelkel@tvicorp.com. If Tenant timely submits such punch-list, then
Landlord will complete the repair of the punch-list items within thirty
(30) business days of receipt of such list (which time shall be extended for
delays beyond Landlord’s reasonable control, but in no event longer than sixty
(60) days of receipt of the punch-list). Landlord shall also be responsible for
repairs to latent defects to the Improvements and shall warrant the Improvements
for a period of one (1) year following Substantial Completion. Tenant shall
receive the benefit of any applicable manufacturer’s warranties, to the extent
such warranties are assignable to Tenant, and, if not assignable, then
Landlord’s warranty described in the preceding sentence shall be for the period
of the applicable manufacturer’s warranty, but in no event less than one
(1) year.

(g) The parties acknowledge that Landlord’s ability to complete the Improvements
to the Renovated Premises is dependent upon Landlord obtaining unfettered access
to the Renovated Premises and reasonable access to the remainder of the Premises
as may be reasonably required to complete the Improvements and bring equipment
and supplies to the Renovated Premises. Tenant is currently occupying the
Premises, and Tenant agrees to permit Landlord full access to the Renovated
Premises during normal business hours to construct the Improvements; provided,
however, Landlord agrees to use its reasonable best efforts to not cause
interference with the conduct of Tenant’s business while constructing the
Improvements, and, provided Landlord utilizes such reasonable efforts, under no
circumstance will Tenant be entitled to a full or partial abatement of Tenant’s
rental obligations for the Premises during the construction of the Improvements.
Landlord shall cooperate with reasonable requests made by Tenant to avoid
disruption or damage to the filter and canister assembly line being conducted in
the Renovated Premises.

 

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(h) Tenant agrees to hold harmless and indemnify Landlord from any and all
claims, liability, loss or damage including but not limited to damage to
Tenant’s personal property and disruption to Tenant’s business suffered by
Tenant arising from Landlord’s renovation of the Premises, except for damage to
Tenant’s personal property caused by Landlord’s or Landlord’s contractors’ or
subcontractors’ negligence or willful misconduct.

(i) In the event Substantial Completion of the Improvements has not occurred on
or before the sixth (6th) week following the date the Final Plans are approved
by Landlord and Landlord has obtained all necessary permits to complete the
Improvements, then for each week, or portion thereof, thereafter that
Substantial Completion has not occurred, the March 1, 2009 date for Minimum Rent
to increase to $5.53 per square foot shall be extended by one (1) week. For
example, if the Final Plans are approved on July 1, 2008 and Substantial
Completion of the Improvements occurs on September 1, 2008, then the March 1,
2009 date shall be changed to March 22, 2009, a three (3) week extension
corresponding to two additional full weeks and one additional partial week, in
excess of six (6) weeks, that Landlord required for Substantial Completion of
the Improvements. After full execution of this Amendment, the Landlord will
promptly apply for and use its diligent good faith efforts to obtain all
necessary permits to complete the Improvements and substantially complete the
Improvements in a timely and prompt manner.

NOTICES TO LANDLORD. Notwithstanding the provision of the Lease to the contrary,
all notices or demands shall be provided to Landlord at the following address:

Glenn Dale Business Center, L.L.C.

c/o First Potomac Management LLC

Attn.: Tim Zulick

7600 Wisconsin Avenue, 11th Floor

Bethesda, Maryland 20814

REPRESENTATIONS. Landlord and Tenant hereby acknowledge that the Lease is in
full force and effect. Tenant acknowledges as of the date of Tenant’s execution
of this Amendment that, to Tenant’s actual knowledge, Landlord has met all of
its obligations under the Lease, except for the outstanding items listed in
Paragraph 4 of this Amendment, and Landlord is not currently in default under
the Lease. Landlord acknowledges that, to the best of Landlord’s knowledge,
Tenant is not currently in default under the Lease.

RATIFICATION. Unless a term or condition of the Lease is expressly contradicted
by the terms of this Amendment or modified hereby, all terms and conditions of
the Lease shall remain in full force and effect and continue to bind Landlord
and Tenant. In the event that a term of this Amendment is fundamentally
inconsistent with a term of the Lease, the terms of this Amendment shall
control. The terms of the Lease, as modified hereby, are ratified and affirmed
by the parties.

 

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ENTIRE AGREEMENT. This Amendment constitutes the entire agreement of the parties
with respect to the subject matter addressed herein. No terms, conditions,
representations, warranties, promises, or understandings, of any nature
whatsoever, express or implied, have been made or relied upon by any party
hereto. This Amendment may not be modified, waived, discharged or terminated
other than by a writing executed by the parties hereto.

BROKER. Landlord and Tenant each represent and warrant to the other that it has
not employed any broker, agent or finder with regard to this Amendment except
First Potomac Management LLC, which broker will be paid pursuant to a separate
agreement with Landlord, and each party hereby indemnifies and holds harmless
the other for any other claims relating to commissions or brokerage fees arising
from a breach of the above warranty.

AUTHORITY. The parties hereto: (i) agree to execute any and all documents, and
to take any other action, that may be necessary to carry out the express terms
and intent of this Amendment; (ii) represent that the individuals executing this
Amendment on behalf of Landlord and Tenant are duly authorized and empowered to
execute this Amendment; and (iii) agree that this document shall not be
construed against any party due to said party drafting this Amendment. This
Amendment may be executed in counterparts.

BINDING EFFECT. The terms of this Amendment shall be binding upon the parties
hereto and their respective successors and assigns.

IN WITNESS WHEREOF, the parties hereto set forth their hands and seals as of the
date first set forth above.

 

WITNESS/ATTEST:   LANDLORD:  

Glenn Dale Business Center, L.L.C.,

a Maryland limited liability company

    By:  

Greenbrier/Norfolk Investment LLC

Its Sole Member

    By:  

Greenbrier/Norfolk Holding LLC

Its Sole Member

    By:  

First Potomac Realty Investment

Limited Partnership

Its Sole Member

    By:  

First Potomac Realty Trust

Its General Partner

/s/ Timothy M. Zulick                   By:  

/s/ James H. Dawson

    Name:  

James H. Dawson

    Title:  

EVP

    Date:  

6/18/08

 

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WITNESS/ATTEST:   TENANT:  

TVI Corporation,

a Maryland corporation

/s/ Sean R. Hunt                   By:  

/s/ Sherri Voelkel

    Name:  

Sherri Voelkel

    Title:  

SVP and CFO

    Date:  

6/16/08

 

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EXHIBIT A

Preliminary Working Drawings and Specifications

[To be attached when finalized and approved by Landlord and Tenant]

 

A-1

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EXHIBIT B

Project Budget

[OMITTED]

 

B-1