Sources of Contamination in Manufacturing

Compressor contamination can occur for many different reasons. This comprehensive webinar by our president Ruby Ochoa discusses compressor contamination and how it can occur. Manufacturers of food, pharmaceuticals, medical devices and much more will find many useful tips to avoiding contamination in this lesson. Feel free to contact us directly for your ISO 8573, SQF, BRC and BCAS compressed air testing needs.

Compressor Contamination and How It Occurs

Intake Air

Intake Contamination may Include:

  1. Particles (viable & nonviable)
  2. Water Vapor
  3. Oil Vapor
  4. Gases
Primary sources of contamination in a compressed air supply include the ambient intake air and the compressor itself. At any given time the atmospheric air feeding the compressor inlet may have contaminants such as solid particles (dirt, sand, soot, metal oxides, salt crystals), water vapor, oil vapor, and microorganisms. Careful consideration should be given to the placement of the compressor intake to avoid these contaminants as much as possible. The intake filter as a first defense should be routinely monitored and replaced according to the manufacturer’s guidelines.


Contaminants Created by the System Itself

  1. Wear Particles
  2. Intake Water can cause corrosion
    1. Damaging equipment
    2. Promote microbial growth
    3. Ruin the final product

Oil-free Compressors

  1. Can still have oil issues from oil introduced by the intake

Gases Possibly Created by the Compressor

  1. Carbon Monoxide
  2. Carbon Dioxide
  3. Gaseous Hydrocarbons
The compressor, if oil lubricated, can add oil in the form of liquid, aerosol, or vapor. Any compressor that is improperly maintained can be a source of contamination. Other sources of contamination include the system piping and air storage receivers.

Human Error

Potential air quality problems can arise from misuse, mishandling, inattention to maintenance, and human error.


New piping should be tested to assure that it has been properly purged of potential contaminants such as particulates, solders, or glues used during installation. Older piping can have an accumulation of water, rust, and oil. When connecting new piping to an older piping distribution system, the jarring of the old piping can cause particulates (such as rust, pipe scale, dirt, metal oxides, etc.) to be loosened and introduced into the new piping.Storage receivers with excess water (vapor, liquid, or a mixture of oil and water) can become a breeding ground for microorganisms.


A periodic air test program can provide critical information to monitor air quality degradation and help in the prevention of product contamination. The sampling plan should include sampling points, a statistically significant number of samples, and a frequency of sampling that will monitor all conditions that could affect the quality of air such as environmental conditions, maintenance schedules, and production activity. “The number of samples should be adequate to provide sufficient statistical confidence of quality.” [CGMP Guidance for Industry Process Validation: General Principles and Practices.]

Air Specifications

The tables below show the compressed air specifications as outlined by the BCAS and ISO 8573:2010. Many manufacturers establishing SOPs for compressed air used in the manufacturing process refer to these specifications to help establish their own guidelines.

BCAS Food and Beverage Grade Compressed Air
Best Practice Guideline 102

ISO 8573-1:2010
Purity Class
Particles (P)WaterOil
By Particle Size
(maximum number of particles per m3)
Vapor Pressure DewpointAerosol & Vapor
0.1 µm < d ≤ 0.5 µm0.5 µm < d ≤ 1.0 µm1.0 µm < d ≤ 5.0 µm°C°Fmg/m3
Direct Contact
400,0006,000100≤ -40≤ -40≤ 0.01
Indirect Contact
400,0006,000100≤ +3≤ +37≤ 0.1
Microbial ContaminantsHazard analysis shall establish the risk of contamination by microbiological contaminants from compressed air. The level of control identified as being required over microbiological contaminants in the compressed air shall be detected using the test method specified in ISO 8573-7.
Footnotes(P) Particle classes 1-5 may not be employed if particles >5 micron are present according to ISO 8573-1.
Air & Gas Specifications referenced above may be viewed and/or purchased from: BCAS - British Compressed Air Society

ISO 8573-1:2010 Compressed Air Contaminants and Purity Classes

By Particle Size
(maximum number of particles per m3) See Note 2
By MassVapor Pressure DewpointLiquidLiquid, Aerosol, & Vapor
See Note 1
0.1 µm < d ≤ 0.5 µm0.5 µ m< d ≤ 1.0 µm1.0 µm < d ≤ 5.0 µmmg/m3°C°Fg/m3mg/m3
0As specified by the equipment user or supplier and more stringent than class 1
1≤ 20,000≤ 400≤ 10-≤ -70≤ -94-≤ 0.01
2≤ 400,000≤ 6,000≤ 100-≤ -40≤ -40-≤ 0.1
3-≤ 90,000≤ 1,000-≤ -20≤ - 4-≤ 1
4--≤ 10,000-≤ +3≤ +37-≤ 5
5--≤ 100,000-≤ +7≤ +45--
6---0 – ≤ 5≤ +10≤ +50--
7---5 – ≤ 10--≤ 0.5-
8------≤ 5-
9------≤ 10-
X---> 10--> 10> 5
 Microbiological ContaminantsOther Gaseous Contaminants
 No purity classes are identifiedNo purity classes are identified
Gases mentioned are: CO, CO2, SO2, NOX, Hydrocarbons in the range of C1 to C5

Note 1: ISO 8573 Oil includes aerosol, vapor in the range of C6+, and liquid oil. Liquid oil is typically sampled when wall flow is present, contamination is suspected, or results are greater than 5 mg/m3. Trace can provide a separate kit for liquid oil testing.

Note 2: For Particle Class 0, 1, & 2 (0.1 - 0.5 µ range only), a laser particle counter with a high-pressure diffuser is required. Rental of this equipment is available on a reservation basis. Contact us for details. To qualify for Particle Classes 0 through 5, there can be no particles greater than 5µ present.

In some cases, Trace uses alternative sampling techniques or analytical methods to those specified in ISO 8573, for details see Smith White Paper, 2012.

Air & Gas Specifications referenced above may be viewed and/or purchased from: ANSI - American National Standards Institute