Interpretation ID: aiam1995
Chief Engineer
Construction Machinery Company
P.O. Box 120
Waterloo
IA 50704;
Dear Mr Johnson: This responds to your June 18, 1975, question whether a system whic pressurizes a water tank on a concrete mixer by means of air from the truck's air brake system would violate the requirements of Standard No. 121, *Air brake systems*.; The answer to your question is no. Standard No. 121 does not contain prohibition on the use of air pressure from the air brake system for powering auxiliary devices. The vehicle must of course conform to Standard No. 121 following installation of the device if the installation occurs prior to the first purchase in good faith for purposes other than resale.; Although not a requirement of the standard, the National Highwa Traffic Safety Administration does consider it appropriate that a pressure protection valve be placed in the line to the auxiliary device so that a rupture of an auxiliary line does not cause depletion of air pressure in the brake system.; Sincerely, Frank A. Berndt, Acting Chief Counsel