CLS Extraction Explained for Cannabis Concentrates

Written by Lorien Strydom

February 6th, 2026

You've seen the term "CLS extraction" and wondered if it's safe, how it works, and whether those 97% pure THCA diamonds at the dispensary are legitimate.

The confusion makes sense—closed-loop systems represent sophisticated extraction technology that sits at the intersection of chemistry, engineering, and cannabis cultivation.

This guide breaks down exactly how CLS extraction creates concentrates like wax, shatter, live resin, and THCA diamonds while maintaining safety standards through sealed, pressurized systems.

We'll walk through the mechanics, address solvent concerns head-on, and show you how to read test results that separate quality products from questionable ones.

Table of Contents

• What Is CLS Extraction?
• How Closed-Loop Systems Work
• The Step-by-Step Extraction Process
• Solvents Used in CLS Extraction
• Temperature and Pressure Management
• Safety Standards and Compliance
• Quality Indicators: Reading COAs
• CLS vs Other Extraction Methods
• Creating Premium Products Like THCA Diamonds
• FAQs About CLS Extraction

What Is CLS Extraction?

Closed-loop system extraction refers to a sealed, pressurized method of pulling cannabinoids and terpenes from cannabis using hydrocarbon solvents or ethanol. The "closed-loop" designation means solvents stay contained within the system rather than being released into the atmosphere, with recovery rates reaching 95% or higher.

This process creates concentrated cannabis products including oils, wax, shatter, live resin, and crystalline structures like THCA diamonds. The sealed environment prevents solvent loss, protects operators from exposure, and reduces environmental impact compared to open-loop methods that vent solvents directly into the air.

Safety comes from system design rather than solvent elimination. Professional extraction facilities use specialized equipment that contains hydrocarbon solvents throughout the entire process, preventing the explosion risks and environmental hazards associated with open blasting.

Brands like Mood partner with certified extraction facilities to create products like their 97.85% pure THCA diamonds. These partnerships ensure quality control and safety compliance without requiring cannabis brands to operate complex extraction equipment themselves.

How Closed-Loop Systems Work

Closed-loop extractors consist of several connected vessels: a material column for cannabis, solvent tanks, collection chambers, and recovery pumps. These components remain sealed and pressurized throughout the extraction process, creating a complete circuit where solvents move but never escape.

The system operates through pressure differentials rather than open venting. Chilled solvents in liquid form move through packed cannabis material, dissolving cannabinoids and terpenes as they pass. The solution then transfers to a collection vessel where gentle heat evaporates the solvent, leaving concentrated oil behind.

Passive vs Active Systems

Passive CLS systems rely entirely on pressure and temperature differentials to move solvents without mechanical pumps. These simpler setups work well for smaller operations but require careful monitoring to maintain proper flow rates and extraction efficiency.

Active systems incorporate pumps and automated controls that precisely manage solvent movement, temperature, and pressure throughout the run. These systems handle larger throughput and provide more consistent results, though they carry higher equipment costs and maintenance requirements.

C1D1 Facility Classification

Professional extraction facilities operate in C1D1 (Class 1, Division 1) classified spaces designed for environments where flammable vapors may be present. This classification requires explosion-proof electrical equipment, proper ventilation systems, and strict protocols for solvent handling.

Cannabis brands like Mood don't operate extraction equipment directly. Instead, they partner with specialized facilities that maintain C1D1 compliance, ASME-certified pressure vessels, and trained technician staff to ensure quality and safety standards meet or exceed industry requirements.

The Step-by-Step Extraction Process

Understanding the extraction workflow clarifies how raw cannabis becomes concentrated products. Each stage requires precise timing and environmental control to maximize cannabinoid recovery while preserving delicate terpene compounds.

Material Preparation and Loading

Fresh-frozen or dried cannabis gets packed into the material column with attention to density. Packing too loosely allows solvent to channel through gaps without fully saturating the material. Overpacking restricts flow and leaves pockets of unextracted cannabinoids.

Professional operators aim for 70-80% column capacity, creating consistent contact between solvent and plant material. The column temperature drops below freezing before solvent introduction to preserve volatile terpenes that would otherwise evaporate.

Solvent Introduction and Saturation

Chilled solvent—typically butane cooled to -20°F to -40°F—enters the material column in liquid form. The cold temperature keeps the solvent liquid under pressure while preventing terpene loss from heat exposure.

The soak or stall phase allows time for solvents to penetrate plant structures and dissolve target compounds. Short soak times of 5-10 minutes work for most extractions, though extended soaks can pull additional cannabinoids from difficult-to-extract material.

Separation and Collection

Solvent carrying dissolved cannabinoids and terpenes transfers from the material column to a collection vessel. This separation relies on pressure differentials—the collection chamber operates at lower pressure, drawing the cannabinoid-rich solution away from spent plant material.

The solution separates into concentrate and solvent through gentle heating. As temperature rises in the collection vessel, solvent evaporates and moves toward the recovery system while concentrated oil remains behind.

Solvent Recovery and Reuse

Recovery pumps pull vaporized solvent from the collection chamber and condense it back into liquid form for reuse. Effective recovery requires drawing vapor faster than it's generated, maintaining low pressure in the collection vessel while condensing recovered solvent in refrigerated tanks.

Quality closed-loop systems recover 95-98% of solvents used, turning what was once a consumable expense into a reusable resource. This recovery efficiency makes professional CLS extraction both economically viable and environmentally responsible.

Secondary Refining for Premium Products

Raw extract undergoes additional processing to create specific concentrate textures and purities. Winterization removes plant waxes and lipids by dissolving the extract in ethanol and freezing it, causing waxes to solidify for filtration.

Some facilities use color remediation columns (CRC) to filter extracts through silica and activated carbon, removing pigments and residual impurities. For ultra-premium diamonds like Mood's 97.85% pure THCA crystals, extended crystallization periods of days or weeks create the distinctive diamond structures through controlled supersaturation.

Solvents Used in CLS Extraction

Different solvents extract cannabinoids with varying efficiency and selectivity. The solvent choice influences final product texture, flavor profile, and cannabinoid concentration rather than determining safety—proper equipment and protocols create safe products regardless of solvent type.

Butane: The Industry Standard

N-butane and isobutane dominate cannabis extraction for their efficient cannabinoid dissolution and low boiling point of 31°F. These properties allow complete solvent recovery at gentle temperatures that preserve heat-sensitive terpenes.

Butane extractions create the full range of concentrate textures including shatter, wax, sauce, and crystalline diamonds. The solvent's selectivity means it pulls cannabinoids and terpenes preferentially while leaving behind plant waxes and chlorophyll.

Propane: Light Hydrocarbon Extraction

Propane's lower boiling point of -44°F enables even colder extraction temperatures, capturing highly volatile terpenes that butane might miss. Some extractors use propane blends with butane to balance extraction efficiency with terpene preservation.

Pure propane extractions tend toward lighter, more liquid consistencies. These products appeal to consumers seeking pronounced flavor profiles and effects from volatile aromatic compounds.

Ethanol: Scalable and Regulatory-Friendly

Food-grade ethanol extraction scales efficiently for large operations and carries fewer regulatory burdens than hydrocarbon methods. The solvent extracts cannabinoids effectively but also pulls chlorophyll and plant waxes, requiring additional refinement steps.

Ethanol's selectivity differs from hydrocarbons—it extracts a broader range of compounds including water-soluble constituents. This creates full-spectrum extracts that retain more of the plant's original compound profile.

CO2: Alternative Pressure-Based Extraction

Supercritical CO2 extraction operates through pressure manipulation rather than chemical dissolution. At specific temperature and pressure combinations, CO2 behaves as both liquid and gas, penetrating plant material while dissolving target compounds.

The method produces clean extracts without hydrocarbon residues, though terpene preservation requires careful parameter control. Many operators add terpenes back after extraction to restore flavor profiles that high-pressure processing diminishes. Learn more about CO2 extraction methods and their applications.

Solvent Safety: Process Over Chemistry

Safety stems from closed-loop containment and proper testing rather than solvent choice itself. Butane and propane become safe through sealed systems, trained operators, and residual solvent testing that verifies final products contain negligible traces.

Residual solvent testing measures remaining solvents in parts per million (ppm). Legal markets set maximum allowable residuals—typically 5,000 ppm for butane and 5,000 ppm for propane, though many quality products test far below these thresholds.

Temperature and Pressure Management

Precise environmental control separates quality extraction from wasteful processes. Temperature affects terpene preservation, while pressure differentials drive solvent movement through the closed-loop system without requiring mechanical pumps in passive configurations.

Cold extraction temperatures between -20°F and -40°F preserve volatile terpenes that vaporize at room temperature. Butane's low boiling point means it remains liquid at these temperatures under pressure, dissolving cannabinoids efficiently while protecting delicate aromatic compounds.

Practical Temperature Control Techniques

Dry ice chillers wrap around material columns and solvent tanks, maintaining subzero temperatures throughout the extraction. Some systems use hot water jackets on collection vessels to gently evaporate solvents without scorching concentrated oils.

The temperature differential between cold extraction chambers and warmer collection vessels creates natural convection that moves vaporized solvents toward recovery condensers. This passive movement reduces mechanical complexity while maintaining efficient solvent recovery.

Pressure Differentials Drive Flow

Pressure manipulation moves solvents through closed-loop systems without direct pumping. The material column operates at higher pressure than collection vessels, creating flow from high to low pressure zones as extraction progresses.

Recovery systems operate at the lowest system pressure, pulling vaporized solvents away from collection vessels toward refrigerated condensers. This pressure cascade creates continuous solvent circulation throughout multi-hour extraction runs.

Diamond Formation Requires Extended Control

Creating crystalline THCA diamonds demands weeks of precise temperature manipulation. Operators slowly reduce solution temperature to create supersaturation where THCA molecules exceed solubility limits and crystallize out of solution.

The extended time frame allows large, clear crystals to form rather than the cloudy, small-grain structures that rapid crystallization produces. Mood's 97.85% pure diamonds represent the precision control that professional extraction facilities achieve through patient, temperature-managed crystallization.

Safety Standards and Compliance

Professional extraction facilities operate under strict safety protocols that separate legal, compliant operations from dangerous amateur setups. These standards protect workers, ensure product quality, and maintain the industry's credibility with regulators.

Electrical and Facility Requirements

C1D1 electrical classifications mandate explosion-proof equipment, sealed conduits, and grounding systems designed for environments where flammable vapors may exist. All electrical components—from light fixtures to control panels—must meet these specifications to operate legally.

Ventilation systems maintain negative air pressure in extraction rooms, directing any potential vapors toward detection systems and exhaust paths. Gas detection monitors continuously measure hydrocarbon concentrations, triggering shutdowns and alarms if readings approach dangerous levels.

Pressure Vessel Certification

ASME (American Society of Mechanical Engineers) certification verifies that pressure vessels can safely contain the forces generated during extraction. Each certified vessel undergoes pressure testing, material verification, and weld inspection before receiving its stamp.

Annual inspections and pressure testing maintain certification validity. Facilities document these tests, creating audit trails that prove ongoing compliance with safety standards.

Operator Training and Protocols

Trained technicians follow written standard operating procedures for every extraction run. These protocols detail equipment setup, parameter monitoring, emergency shutdown sequences, and proper solvent handling from storage through recovery.

Professional extraction facilities maintain training records, incident logs, and maintenance schedules that demonstrate systematic safety culture. Cannabis brands evaluating extraction partners look for these documentation systems as evidence of reliable quality control.

Residual Solvent Testing Requirements

Parts per million (ppm) measurements quantify residual solvents in final products. A reading of 5,000 ppm means 0.5% of the product weight consists of residual solvent—small enough to be considered safe but high enough to require proper purging.

Licensed cannabis markets enforce mandatory residual solvent testing on all concentrate products. Hemp-derived products face less consistent enforcement, making third-party testing and COA transparency critical for consumer safety.

Testing Standards Across Markets

State-licensed cannabis programs require residual solvent panels on all concentrate products before retail sales. Labs test for butane, propane, ethanol, and other potential solvents using gas chromatography methods that detect trace levels accurately.

Hemp-derived products like Mood's THCA diamonds voluntarily undergo the same rigorous testing even though federal regulations don't mandate it. This transparency demonstrates quality commitment and gives consumers confidence in product safety.

Quality Indicators: Reading COAs

Certificates of Analysis (COAs) provide objective verification of concentrate quality and safety. Learning to read these lab reports empowers consumers to make informed purchasing decisions based on actual test results rather than marketing claims.

Every legitimate concentrate product includes access to a COA through QR codes, batch numbers, or online databases. If a brand doesn't provide easy COA access, consider that a red flag regardless of price or packaging quality.

Potency Panels Show Cannabinoid Content

Cannabinoid testing reveals the concentration of THC, THCA, CBD, and minor cannabinoids in percentage terms. A product testing at 97% THCA contains 970mg of THCA per gram—information that directly informs serving size and expected effects.

Total potential THC calculations convert THCA percentages to their activated THC equivalent. Since THCA becomes more potent when heated, multiplying THCA percentage by 0.877 estimates the active THC content after consumption.

Residual Solvent Testing Verifies Safety

Residual solvent panels list every solvent tested and their measured concentrations in ppm. Quality products show "ND" (not detected) or readings well below maximum allowable limits of 5,000 ppm for most solvents.

Butane, propane, ethanol, and methanol all require testing in hydrocarbon-extracted products. The absence of residual solvent testing on a concentrate product's COA should raise immediate concerns about processing standards.

Additional Safety Testing

Comprehensive COAs include heavy metal testing (lead, arsenic, cadmium, mercury), pesticide screening for agricultural chemicals, and microbial testing for mold, bacteria, and other contaminants. These panels verify safety beyond just residual solvents.

Terpene profiles on quality COAs list individual aromatic compounds and their concentrations. This information explains flavor characteristics and suggests entourage effect potential when terpenes and cannabinoids work together synergistically.

Verification and Date Checking

Match the batch number on your product label to the COA batch number. Any mismatch means you're viewing test results for a different batch that might have significantly different potency or quality characteristics.

Test dates matter—COAs older than 90 days raise questions about product freshness and inventory turnover. Mood maintains current COA access for all products, demonstrating transparent quality control and regular testing schedules. Learn more about Mood's third-party testing process and how we ensure product quality.

CLS vs Other Extraction Methods

No single extraction method proves universally superior. Each technique creates specific product characteristics and serves different market segments based on desired outcomes rather than inherent quality hierarchies.

Solventless Rosin: Mechanical Pressure

Rosin extraction applies heat and pressure to cannabis without any solvents. The mechanical pressing squeezes cannabinoid-rich oils from trichome glands, creating concentrates that appeal to consumers who prefer to avoid solvent-based products entirely.

Rosin typically tests at 60-80% total cannabinoids compared to 90%+ achievable with hydrocarbon methods. The trade-off is simple: solventless processing for broader compound retention versus higher purity through selective solvent extraction.

CO2 Extraction Differences

Supercritical CO2 creates clean extracts without hydrocarbon residue concerns, appealing to consumers prioritizing non-flammable processing. The method's different selectivity profile extracts compounds in ratios distinct from hydrocarbon results.

CO2 extraction often strips terpenes during high-pressure processing, requiring reintroduction for flavor restoration. Hydrocarbon methods preserve terpenes naturally when operators maintain proper temperature controls throughout extraction.

Open-Loop vs Closed-Loop Comparison

Open-loop extraction systems vent solvents directly into the atmosphere after passing through cannabis material. These setups create fire and explosion risks while wasting expensive solvents and releasing volatile organic compounds into the environment.

Closed-loop systems contain solvents throughout the process, recovering 95%+ for reuse. This containment eliminates explosion risks from vapor accumulation, reduces operating costs through solvent reuse, and prevents environmental contamination.

Purity Achievement Through CLS

The highest-purity concentrates come from hydrocarbon CLS extraction followed by extended refinement. Mood's 97.85% pure THCA diamonds demonstrate what professional closed-loop operations achieve through patient crystallization and proper technique.

Other methods serve valid purposes—rosin for solventless products, CO2 for specific applications, ethanol for scale—but hydrocarbon CLS remains the reference standard for creating ultra-pure crystalline concentrates.

Creating Premium Products Like THCA Diamonds

THCA diamonds represent the pinnacle of CLS extraction mastery. Creating these crystalline structures requires extending the basic extraction process into weeks-long crystallization phases with precise environmental control throughout.

The process begins with quality hydrocarbon extraction producing a solution supersaturated with THCA. Rather than quickly purging solvents, operators maintain this supersaturation while slowly reducing temperature over days or weeks.

Crystallization Through Supersaturation

As solution temperature drops gradually, THCA molecules exceed their solubility limits and begin forming crystalline structures. Slow temperature reduction allows large, clear crystals to grow as individual THCA molecules find optimal positions in the developing lattice structure.

Fast crystallization produces small, cloudy crystals with lower purity. Patient, controlled growth creates the clear, gem-like formations that define premium diamond products.

Separation From Terp Sauce

During crystallization, terpenes and remaining cannabinoids separate from pure THCA crystals, forming the aromatic liquid called terp sauce or diamonds-in-sauce products. Some producers recombine these components, while others sell isolated diamonds separately.

Pure diamond crystals like Mood's 97.85% THCA product contain minimal terpenes, creating concentrated potency that consumers can customize by adding strain-specific terpenes or mixing with other concentrates for flavor enhancement.

Purity Through Process Control

Achieving 97%+ purity requires eliminating impurities throughout the entire extraction and crystallization timeline. This means starting with quality cannabis, maintaining clean equipment, controlling temperature precisely, and allowing adequate time for complete crystallization.

The purity percentage directly reflects process mastery rather than special equipment or proprietary techniques. Any extraction facility with proper closed-loop systems, trained staff, and patience can create high-purity diamonds—but few maintain the standards necessary for consistent 97%+ results.

Quality Verification for Diamond Products

Premium diamond products include comprehensive third-party testing showing cannabinoid purity, residual solvent levels, and absence of contaminants. Brands like Mood demonstrate quality through transparent COA posting rather than vague marketing claims.

Visual inspection helps too—clear, large crystals indicate proper crystallization, while cloudy or small-grain formations suggest rushed processing. But COA verification remains the only reliable way to confirm actual purity percentages.

FAQs About CLS Extraction

Is CLS extraction safe?

CLS extraction is safe when performed in properly equipped facilities by trained technicians following established protocols. The closed-loop design contains solvents throughout the process, preventing vapor accumulation that creates explosion risks in open systems.

Safety comes from sealed equipment, C1D1 electrical systems, ventilation controls, gas detection monitoring, and comprehensive testing that verifies residual solvents in finished products remain below established safety thresholds.

What solvents are safest for CLS?

No solvent is inherently "safer" when proper closed-loop systems and testing protocols are followed. Butane, propane, ethanol, and CO2 all create safe products when extraction facilities maintain sealed systems and test final products for residual solvent levels.

Focus on COA verification rather than solvent type. Products with comprehensive third-party testing showing residuals at or below detection limits demonstrate quality regardless of which solvent was used.

How do I know if residual solvents are at safe levels?

Check the product's COA for residual solvent testing results measured in parts per million (ppm). Readings under 5,000 ppm for butane and propane meet regulatory safety standards in most markets, though quality products often test at "ND" (not detected) or trace levels below 500 ppm.

If a concentrate product doesn't include residual solvent testing on its COA, consider that product questionable regardless of other quality claims. Legitimate extraction operations test every batch for residual solvents as part of standard quality control.

What's the difference between diamonds and other concentrates?

THCA diamonds are crystalline structures of nearly pure THCA reaching 95-99% concentration. Other concentrates like wax, shatter, and live resin contain mixed cannabinoids, terpenes, and residual plant compounds that create more complex effects and lower total purity.

Diamonds provide concentrated potency that consumers can customize by adding terpenes or mixing with other products. Full-spectrum concentrates offer more complete entourage effects through their broader compound profiles. Neither approach is superior—they serve different preferences.

Do hemp-derived products use the same extraction methods?

Yes, hemp-derived concentrates like Mood's THCA diamonds use identical closed-loop extraction methods as products from licensed cannabis markets. The extraction process doesn't differ—only the plant's compliance with federal THC limits distinguishes hemp from marijuana under current regulations.

Quality hemp processors follow the same safety standards, equipment certifications, and testing protocols as licensed cannabis facilities. The distinction matters for legal compliance rather than extraction technique or product quality.

Understanding CLS Extraction Builds Consumer Confidence

Closed-loop extraction creates safe, high-purity cannabis concentrates through sealed systems that contain solvents and recover them for reuse. The method produces everything from basic oils to ultra-premium diamonds through process control rather than equipment sophistication.

Quality verification relies on comprehensive third-party testing that includes residual solvent panels, not just potency numbers. COAs provide objective evidence of safety and purity that marketing claims cannot match.

Mood demonstrates quality commitment through transparent testing, partnerships with certified extraction facilities, and consistent product excellence like 97.85% pure THCA diamonds. Their approach proves that hemp-derived products can meet or exceed the standards set in licensed cannabis markets when brands prioritize testing and transparency.

Mood offers millions of users hemp-derived THC, which is 100% legal and fully compliant cannabis. You may have heard that the legality of hemp-derived THC is currently under attack, which could threaten the wellness of so many. Read here to learn how to join the fight, and help us keep hemp cannabis accessible to all for a long time to come.

Explore Mood's selection of premium concentrates to experience the quality that professional CLS extraction delivers when executed with precision and verified through comprehensive testing.