NOTE This standard covers general-service compressed air systems for shop, laboratory, light-industrial, institutional, healthcare-support, and government facility applications. (1.1)

NOTE General-service compressed air is the utility air that powers pneumatic tools, actuators, laboratory apparatus, blow-off and cleaning stations, and instrument loops throughout a facility. It is generated by one or more compressors, conditioned by a treatment train, accumulated in a receiver, and distributed through fixed piping to terminal outlets. This standard addresses the complete system as a coordinated assembly rather than as isolated pieces of equipment, because the air quality delivered at any outlet is the product of every upstream component working together. (1.2)

NOTE A compressed air package specified only as a compressor leaves the air quality, storage, and distribution undefined, which is the most common source of underperforming installations. Treating the system as a whole is what lets the engineer hold a purity class at the point of use. (1.4)

NOTE This standard applies to new construction and to expansions of existing compressed air systems. (1.5)

NOTE This standard applies to systems operating at pressures up to 200 psig typical facility service. (1.6)

NOTE General-service headers operate at 90 to 125 psig; specialty high-pressure headers may reach 200 psig. Pressures above 150 psig, or piping located in process-classified areas, shift the governing piping code from ASME B31.1 to ASME B31.3 and are addressed accordingly within this standard. (1.7)

NOTE Medical air and dental air piped to patient care areas under NFPA 99 Level 1 are excluded and are governed by Medical Gas Systems. (1.8)

NOTE Level 1 medical air is a life-safety system with its own source equipment, alarms, certification, and dedicated piping. It must never share source equipment or distribution with general-service air. (1.9)

NOTE Breathing air for respiratory protection (OSHA 29 CFR 1910.134 Grade D) is excluded; it is a distinct safety classification with its own purity, monitoring, and alarm requirements. (1.10)

NOTE Fuel gas, natural gas, propane, process piping above 200 psig, and air-driven specialty outlets are excluded and are covered by their respective standards. (1.11)

NOTE See Natural Gas Piping, Fuel Gas Piping, and Plumbing Specialties. Pneumatic HVAC controls tied into the building automation system are covered by Hvac Controls Instrumentation. (1.12)

NOTE ANSI/CAGI B19.1 governs compressor system safety (controls, guarding, relief sizing) while ASME BPVC Section VIII governs the pressure vessel; the two are complementary and both apply. (2.3)

NOTE ISO 8573-1 is referenced for purity classification; the latest adopted edition applies, as the standard has been under revision. (2.4)

NOTE OSHA 29 CFR 1910.169 makes ASME compliance a federal requirement for air receivers, and any receiver of 1.5 cubic feet or larger operating above 15 psig must carry the ASME code stamp. (4.4)

NOTE Rotary screw and reciprocating compressors derate and the discharge air carries more moisture as inlet and ambient temperature rise. Holding the room below 100°F preserves capacity and keeps the downstream dryer load within its rating. (5.2)

NOTE This guidance follows UFC 3-420-02 and removes both the heat of compression rejected to the room and any heat from air-cooled aftercoolers. (5.4)

NOTE A refrigerated dryer holding a 35°F to 39°F pressure dew point is adequate only where every foot of pipe stays above freezing. Routing 35°F-dew-point air through an unheated space condenses and then freezes water in the line, blocking flow and damaging tools, which is one of the most common field failures. (5.7)

NOTE For general facility service (shops, maintenance, light laboratory) the lubricated rotary screw with a refrigerated dryer is the 80% case: it offers continuous-duty capability, good efficiency, and the lowest installed cost for its capacity. Oil-free machines carry a significant cost premium and are justified only where the application genuinely cannot tolerate any oil carryover. Reciprocating machines remain economical for intermittent-duty shops at lower first cost. (6.2)

NOTE Filtered oil-lubricated machines cannot reliably reach ISO 8573-1 Class 1 oil because oil aerosol and vapor pass through coalescing filters as their efficiency degrades. Specifying a Class 1 oil requirement while scheduling a lubricated machine generates substitution requests and field disputes. The purity requirement and the compressor selection must agree. (6.5)

NOTE Lead-lag control alternates the duty unit to equalize wear and brings the lag unit on for peak demand or as standby. A single compressor leaves the facility without air during any failure or routine service of that one machine. (6.8)

NOTE Single-stage machines are efficient and adequate for general 100 to 125 psig service. Two-stage compression with intercooling is more efficient and reaches higher pressures, which suits high-pressure headers and continuous high-load duty. (6.11)

NOTE A VSD compressor matches motor speed to demand and avoids the unloaded-running and blow-down losses of fixed-speed control. The energy saving is largest where average demand is well below installed capacity; at near-constant full load a fixed-speed load-unload machine is competitive and simpler. (6.14)

NOTE Branch circuit conductors for a continuous-duty motor are sized at not less than 125% of full-load current, and direct-on-line starting draws six to eight times full-load current, which governs disconnect and overcurrent selection. The motor full-load and locked-rotor amperes must be confirmed with the electrical engineer. (6.17)

NOTE The receiver decouples short-duration demand peaks (tool starts, actuator strokes) from compressor output, so the compressor cycles on average demand rather than chasing every transient. It also provides residence time for water and oil to separate from the air and settle to the drain. (7.2)

NOTE A common first-pass rule for variable-demand systems is roughly 1 gallon of receiver volume per SCFM of compressor output; the larger of the two checks governs. This follows the UFC 3-420-02 guideline. (7.5)

NOTE OSHA 29 CFR 1910.169 requires this as a federal mandate. The relief capacity must exceed the compressor's full delivery so the receiver cannot be over-pressured even with the inlet valve fully open. (7.8)

NOTE OSHA 29 CFR 1910.169 requires a drain at the lowest point so accumulated condensate can be removed. An automatic drain may supplement the manual drain but does not replace it for inspection and service purposes. (7.12)

NOTE ISO 8573-1 classifies air independently for solid particles, water (dew point), and oil. A complete train typically comprises an aftercooler and moisture separator at the compressor discharge, a dryer sized for the required dew point, and point-of-use coalescing and particulate filtration. Each contaminant is addressed by the component suited to it; one device does not cover all three. (8.2)

NOTE Typical class assignments by application: general shop and maintenance air at Class 3.4.3 (particles.water.oil); instrument air at Class 2.2.1; general laboratory air at Class 2.2.2; food-contact air at Class 1.2.1 or better. The class drives the dryer dew point and the filtration grades and must be set before the train is selected. (8.4)

NOTE Removing the heat of compression here drops out most of the water as liquid, which the moisture separator captures, so the dryer receives a far smaller moisture load. (8.6)

NOTE This dew point is adequate for general-service air distributed entirely within heated indoor space and is the 80% case for shop and maintenance systems. It is not adequate where any piping is exposed to freezing temperatures. (8.10)

NOTE Desiccant dryers reach −40°F pressure dew point routinely and −100°F for extreme cases. (8.13)

NOTE Coalescing filters remove oil aerosol and fine particulate; a particulate after-filter protects against desiccant fines where a desiccant dryer is used. Filtration grade is selected to meet the ISO class, not over-specified, because each filter stage adds pressure drop. (8.15)

NOTE At compressed air velocities the internal zinc coating flakes off and the particles travel downstream to clog filters, regulators, and tool valves. Black steel (Schedule 40 or 80 per ASTM A53), Type L copper, or modular aluminum are the appropriate choices. (9.4)

NOTE Aluminum modular systems install quickly, have a smooth bore that minimizes pressure drop, and their sealed joints leak far less than threaded steel, which directly reduces the compressor energy wasted feeding a leaky distribution network. (9.6)

NOTE Sizing on average flow alone undersizes the header so that end-of-line tools starve at peak demand. The sizing calculation must check the farthest, highest-demand outlet under simultaneous full load, not just the steady-state condition. (9.9)

NOTE Where part of the facility needs 150 to 200 psig and the rest needs 100 psig, a dedicated high-pressure header fed by a booster, with regulators dropping to general service at the use points, is more efficient than running the whole facility at the higher pressure. (9.11)

NOTE A looped main feeds each branch from two directions, halving the effective length and pressure drop, and reserve capacity built in at construction is far cheaper than retrofitting a larger header later. Calling out a design reserve at the outset is a low-cost hedge against facility growth. (9.13)

NOTE Shop air carries more particulate, moisture, and oil than instrument loops tolerate. Tapping instruments off a shop header contaminates regulators and positioners and degrades control accuracy, so the two services are kept on separate, independently treated headers. (9.15)

NOTE See compressed air distribution plan. (9.18)

NOTE Compressed air condensate accumulates at every cool point in the system. Left in place it carries downstream as slugs of water and, in lubricated systems, oil. The drain method is selected to remove condensate reliably without wasting compressed air. (10.2)

NOTE A timed solenoid drain opens on a schedule whether or not condensate is present, venting compressed air each cycle. A demand drain opens only when a sensed liquid level requires it, eliminating that loss; the energy saving usually repays the higher device cost. (10.5)

NOTE Oily condensate discharged to a sanitary drain violates environmental regulations. The separator must reduce oil content below the local sewer authority limit, which is commonly below 15 mg/L; the actual limit must be confirmed with the authority having jurisdiction. (10.7)

NOTE General-service air is not certified to medical purity and is not monitored or alarmed to NFPA 99 Level 1 requirements. Any physical connection between this system and a medical gas, oxygen, or other piped gas system is prohibited; the prohibition must be stated explicitly on any project touching a healthcare facility so it survives field coordination. See Medical Gas Systems. (11.2)

NOTE Untreated compressors are a chronic source of complaints in occupied buildings because vibration travels through the slab and piping into walls and ceilings. Isolation at the machine and at every pipe connection interrupts that path. (12.2)

NOTE The flexible connector decouples the rigid distribution piping from the vibrating compressor so that pulsation and vibration are not transmitted into the building piping. (12.5)

NOTE Testing before the piping is buried, insulated, or enclosed allows leaks to be found and corrected while joints are still accessible. (13.2)

NOTE Dew point is the single most common air-quality shortfall and is easily measured at startup with an inline hygrometer; verifying it confirms the dryer is performing to specification. (13.6)

NOTE Adequate clearance around compressors, dryers, and filters is required for filter changes, oil service, and coil cleaning; crowding the equipment guarantees deferred maintenance. (14.2)

NOTE Mains are pitched in the direction of flow and branch takeoffs are taken from the top of the main, so condensate runs to drip legs rather than being carried into the branch. (14.4)

NOTE Pipe ends and equipment connections capped at the factory must stay capped until connected, because debris that enters open piping migrates to filters and valves during startup. (15.2)

NOTE The compression element (airend on a rotary screw, pump on a reciprocating machine) is the highest-value component and many manufacturers offer extended coverage on it; capturing that coverage at purchase protects the largest replacement cost. (16.3)

NOTE Compressors and dryers consume filters, separators, and lubricant on a regular schedule. Delivering a first-year set with the equipment prevents the system from running on degraded consumables while replacements are procured. (17.2)