Instrument air plays a critical role in controlling industrial processes. Its quality directly affects equipment function, process reliability, and plant safety. Yet, across many facilities, misunderstandings about the required standards can cause major system issues. This happens not because the standards are unclear, but because they are often applied without context. In this post, we’ll walk through how these misinterpretations arise, what the real expectations should be, and how to align air quality with actual process demands.
Many Think “Dry and Clean” Means the Same for Every Application
Some operators assume instrument air quality requirements are universal. In truth, standards vary based on the equipment and processes being supported. For example, a pneumatic actuator controlling a water valve might tolerate small amounts of moisture or oil. But a mass flow controller in a precision system cannot.
The confusion often begins when ISO 8573-1:2010 is treated as one-size-fits-all. This standard defines air purity classes for particles, water, and oil, but it doesn’t specify which class is appropriate for a given use. Therefore, facilities must interpret the classes relative to their risk tolerance and device sensitivity.
To avoid misjudgments, we rely on application-based system analysis. This approach looks at where the air is going, how it interacts with other components, and what failure would mean for safety or product quality. It’s better to build the air system from the process backward than to apply an assumed blanket class across the plant.
Over-Specification Can Waste Money and Create Maintenance Challenges
Many facilities aim for higher air quality than needed. This sounds safe but leads to unnecessary energy costs and complex maintenance. If the application doesn’t demand ultra-dry or oil-free air, over-specifying dryers or filtration increases system wear and introduces frequent changeouts.
For instance, adsorption dryers are chosen when a refrigerated dryer would work. The lower dew point may seem like a win, but it forces compressors to run longer and increases purge air consumption. Similarly, adding multiple coalescing filters can cause excessive pressure drop, reducing system efficiency.
Instead of applying maximum filtration, we recommend targeting realistic air quality that aligns with component tolerances. Our industrial air system solutions are always guided by what the equipment actually needs, not what looks good on paper.
Learn more about how we match system design to performance requirements by reviewing our approach to industrial air system solutions.
Misreading Dew Point Requirements Creates Risk in Seasonal Environments
Cold weather introduces another layer of misinterpretation. Some teams see dew point numbers and assume they refer to the air temperature in the plant. However, dew point reflects the temperature at which moisture condenses. That matters most when air travels outdoors or into colder areas.
Facilities located in regions with freezing winters need to consider pipe routing. If air travels outside or into unheated buildings, moisture can freeze inside valves or instruments. That means even if the plant operates at 15°C, the system might require -20°C dew point air in specific lines.
A better approach is to segment air preparation based on where the air goes. Not every line needs extreme dryness. But for external or exposed zones, localized drying or heat tracing might be necessary. That makes the system smarter and avoids over-drying the entire network.
Poor Documentation Causes Long-Term Standard Drift
Over time, many facilities lose track of their original air quality targets. Equipment upgrades, line changes, or staff turnover create gaps in documentation. When that happens, maintenance teams begin using replacement filters or dryers based on availability, not compatibility.
This leads to a mismatch between what the system was built to do and what it currently supports. For example, if a filter rated for 0.01 micron gets swapped for one rated at 1 micron, the air may no longer meet the required standard—especially for sensitive instruments downstream.
To fix this, we build clear documentation into our system reviews. Each filter, dryer, and regulator should be labeled not just with specs, but also with purpose. That ensures replacements and upgrades stay aligned with process needs, not just part numbers.
We offer tools that help define and maintain these specs in practical terms. Explore our support for compressed air reliability planning.
Instrument Air Is Not Always the Same as Plant Air
Operators often treat all compressed air as equal. But plant air typically powers tools, machinery, or bulk handling systems, while instrument air feeds sensitive control elements. The needs are not the same, even if the source is.
Merging both into a single line without separation or point-of-use conditioning can compromise both. For example, lubrication carryover from air tools may reach instrumentation, causing drift or clogging. Or moisture from a poorly drained branch can reach a pneumatic valve and freeze.
To address this, we install dedicated air preparation stages for instrument air. That can include additional filtering, regulated pressure control, or even separate piping. Keeping instrument air isolated ensures consistency and reduces contamination risks.
Filter Selection Should Match Contaminant Type and Location
Different filters target different threats. Coalescing filters remove oil aerosols, but they don’t remove water vapor. Particulate filters stop rust or dust, but they don’t trap vapors or aerosols. This is where interpretation often fails—facilities rely on general filter types rather than matching them to contaminants.
Another issue is placement. A filter installed too far upstream may not protect downstream exposure points. Or, if filters are stacked improperly, the more precise filter might load too quickly because a coarse pre-filter was skipped.
Our team uses system mapping to determine the right filter combinations and spacing. We ensure that coarse filters catch bulk debris, mid-level filters handle moisture and oil, and fine filters are placed close to the most sensitive endpoints.
If you’re unsure about what’s hiding in your pipes, take a look at how our air quality monitoring practices can help you identify risks before they damage equipment.
Operating Pressure Affects More Than Just Flow
Another overlooked factor in interpreting air standards is the role of pressure. ISO 8573 standards are based on a reference pressure. But when systems operate above or below that point, the actual concentration of contaminants per volume changes.
For instance, if a system operates at 6 bar instead of 7 bar, the same amount of oil content becomes more concentrated. That means a system running at lower pressure might need stricter oil removal performance to stay within spec.
To manage this, we factor operating pressure into air quality calculations. We don’t just rely on lab data from new filters—we track system behavior during real operating conditions to see how pressure changes affect air purity.
Leaks and Backflow Can Compromise Clean Zones
Even in well-designed systems, backflow or unnoticed leaks can cause clean air zones to become contaminated. This often happens when isolation valves are left open or older branches backfeed into instrument lines.
One common example is a maintenance hose installed near a control panel. If that hose is fed from plant air instead of conditioned instrument air, contamination can enter the local loop and damage components.
Our strategy involves loop integrity checks and color-coded diagrams so teams can quickly see which lines are safe for use and which are not. This reduces the chance of cross-contamination, especially in emergency or bypass setups.
Automatic Drains Are Often Installed but Rarely Tested
Drains are supposed to remove collected moisture before it moves downstream. However, many are set and forgotten. If they clog or fail, liquid water can pass through the system unnoticed. That turns a clean instrument air loop into a wet mess.
Even drains with timers or sensors need regular functional testing. We often find blocked lines or stuck solenoids that prevent proper discharge. As a result, moisture builds up in filters or lines, slowly degrading air quality.
To keep drains reliable, we use accessible layouts and service-friendly designs that make it easy to check and replace faulty units without shutting down large parts of the system.
FAQs
What does ISO 8573-1 mean for my plant?
It defines levels of air purity but doesn’t tell you which level you need. Your process determines that.
Can I use the same air for tools and instruments?
Not safely. Tools can introduce oil and dirt. Instruments need cleaner, more stable air.
Why is my air still wet even with a dryer?
Check your drain systems, dew point rating, and filter sequence. The dryer may be undersized or misapplied.
How do I know if my air quality is still in spec?
Test it. Use particle counters, oil vapor sensors, and dew point monitors near your critical endpoints.
Should every line have the same filters?
No. Customize filters by application and location. Some need high purity, others do not.
If you’re unsure how to interpret your current setup or want help aligning your air system with actual process needs, reach out to our team for practical guidance and support through our compressed air system consultation service.