TECHNICAL STANDARD
ASTM D4285
Standard Practice for Indicating Oil or Water in Compressed Air
ASTM International
2024
Current
WHAT DOES THIS STANDARD COVER?
Provides a visual technique for determining the presence of oil or water in compressed air used for abrasive blast cleaning, air blast cleaning and coating application.
WHY IS IT RELEVANT?
Relevant when checking that compressed air used during surface preparation and coating operations is clean and dry and is not introducing visible oil or water contamination. This is commonly known as the blotter test. Do not imply that this practice detects every possible contaminant.
KEY INSPECTION CONSIDERATIONS
ASTM D4285 provides a visual technique for indicating the presence of oil or water in compressed air used for abrasive blast cleaning, air cleaning and coating application operations. Clean, dry compressed air is important because oil or water carried by the air supply can contaminate prepared surfaces, abrasive or coating materials. The test is commonly known as a blotter test and is used to assess the compressed-air supply after relevant separators, coolers or driers. The test should be carried out at an appropriate location in the air-delivery system representative of the air being used for the work.
WHAT THE STANDARD SHOULD NOT BE USED TO ASSUME
ASTM D4285 is an indication test for oil or water in compressed air. It should not be treated as a comprehensive chemical analysis of every possible contaminant that may be present in the compressed-air supply. A satisfactory result does not remove the need for appropriate maintenance and operation of compressors, separators, driers and associated equipment. The test also does not establish the cleanliness of the prepared steel surface itself. Surface cleanliness requires separate inspection.
PRACTICAL INSPECTION APPLICATION
ASTM D4285 may be used before and during abrasive blast cleaning or coating application to verify that the compressed-air supply does not show evidence of oil or water contamination. The inspector should identify the air supply being tested, carry out the test at a representative point and record the result. Where contamination is indicated, the cause should be addressed and the suitability of affected surfaces, abrasives or coating operations should be assessed before work proceeds.
RELATED TECHNICAL STANDARDS
RELATED TECHNICAL TOPICS
Compressed air; Surface preparation; Contamination testing
RELATED PIL GUIDANCE
Laser cleaning can remove coatings and corrosion, but the resulting surface must still be inspected and verified against the proposed coating system and project requirements.
RELATED EXPERTISE
Coating Inspection; Testing & Analysis
ABOUT THIS TECHNICAL SUMMARY
Paint Inspection Ltd provides this information to help inspectors, engineers, asset owners and contractors understand the practical relevance of commonly referenced protective coatings standards. This page is PIL technical guidance and does not reproduce or replace the published standard. Users should refer to the current published standard, project specification, coating manufacturer requirements and other applicable contract documents when establishing project requirements or acceptance criteria.
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OFFICIAL STANDARD
PIL technical summaries are intended to explain the inspection relevance of industry standards and do not replace the published document.
STATUS AND SOURCE VERIFICATION
Official ASTM catalogue checked 2026-09-23. ASTM D4285-24 is listed by ASTM as Active. CMS designation, title and edition checked against the official ASTM catalogue record.