Although accurate tests of boiler water for dissolved oxygen are difficult to obtain on board ship, you can be fairly certain of proper oxygen removal by __________.

Correct Answer: Option A — maintaining a normal level of scavenging agents

Direct Winkler or colorimetric dissolved oxygen tests at sea are prone to air contamination errors. Engineers verify adequate deaeration by ensuring a proper reserve residual of chemical oxygen scavengers, such as sodium sulfite or hydrazine, exists in the routine daily boiler water test sample.