From the Senate Appropriations Committee Report, the number appears to be 250 ETD units for FY 2015. The TSA is directed to include recap plans for old units in its FY 2016 Budget Request.
Appropriations Committee
113-198
The Committee recommends $74,000,000 for Explosives
Detection Systems procurement and installation. This is
$10,075,000 below the amount requested and $155,000 above the
amount provided in fiscal year 2014. An additional $250,000,000
in mandatory spending will be available from Aviation Security
Capital Fund [ASCF] fee collections. The total discretionary
and mandatory funding will allow TSA to purchase and install
approximately 109 EDS units and 250 Explosives Trace Detection
[ETD] units in fiscal year 2015. The Committee directs TSA to
include its EDS recapitalization plans within the congressional
budget justification for fiscal year 2016 including detailed
information on expected unit replacements.
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