How to Prepare Herb for a Vaporizer: Manufacturer Table and Storage

Storz & Bickel states in the VEAZY instructions that the finer you grind the herb, the larger its surface area. Arizer advises to grind coarsely, while PAX for one model provides two contradictory guidelines. Therefore, there is no single rule for all vaporizers, and we did not find any reviewed studies on particle size in vaporizers. More reliable data concern the humidity and storage of cannabis herb. The ASTM D8197-22 standard recommends a water activity of 0.55-0.65. The study by Milay et al. from 2020 showed that ground herb loses more terpenes during storage than whole. From this guide, you will learn what the manufacturer of your device says about grinding and portioning, how to store herb, and what to do if mold appears on it.

KEY INFORMATION
• The ASTM D8197-22 standard recommends a water activity of 0.55-0.65 for cannabis herb (ASTM, 2022).
• Manufacturers advise differently on grinding: Storz & Bickel and DynaVap finer, Arizer coarsely. Follow the instructions for your device.
• Grind herb just before the session: ground loses more terpenes than whole (Milay 2020).
• Do not use moldy herb, just dispose of it (Health Canada).

How to Prepare Herb for a Vaporizer According to the Manufacturer?

Preparing the herb depends on the device, as manufacturers provide different, sometimes contradictory guidelines. Storz & Bickel instructs to fill the chamber to the edge in portable devices, Arizer to leave 1-2 mm of space, and DynaVap specifies a portion of 0.1 g. Some companies do not publish any numbers. Therefore, check the instructions for your model before the first session. Below is a summary of what the manufacturers themselves say.

The sources are the user manuals from Storz & Bickel and the Volcano Hybrid page. For PAX, it is the help pages and shortened instructions, for Arizer, the support pages. DynaVap provides data in the FAQ and on the product page, while Topgreen, the manufacturer of X-Max, on the support pages. The grams in the table are solely the manufacturers’ numbers. The portions from reviews and stores are not provided in the table, as manufacturers do not confirm them.

How Fine Should You Grind Herb for a Vaporizer and Why?

As fine as your device’s instructions state, because manufacturers do not agree. Storz & Bickel and DynaVap prefer finer herb. Arizer advises to grind coarsely, while PAX for the FOUR model recommends a medium-fine grind. We did not find any reviewed studies comparing particle sizes of herb in vaporizers. Therefore, there is no universal rule.

Why finer? Storz & Bickel explains in the VEAZY instructions that the finer the ground plant, the larger its surface area. This is the manufacturer’s explanation, not a study result. DynaVap states briefly that finer grinding works better. Arizer goes in the opposite direction: it recommends coarsely ground herb and generally allows whole herb as well.

The most confusion arises with PAX. For FOUR, the manufacturer specifies medium-fine grinding. For Mini 2, its own materials contradict each other. The shortened instructions mention medium-fine grinding, while the advice page states medium, “not fine.” Which version is correct? PAX does not clarify this.

When to grind? Just before the session. In the study by Milay et al. (Frontiers in Plant Science, 2020), all ground samples had lower terpene concentrations after storage than whole flowers. Whole flowers also oxidized less. A grinder is used for grinding, and the Volcano Hybrid includes one in the set. You can find various models in the grinders category, and what to look for when buying is described in the guide grinder for herb: what to choose.

How Tightly Should You Pack the Vaporizer Chamber?

This also depends on the model. Storz & Bickel instructs to fill the chamber of their portable devices to the edge, but without strong packing. PAX FOUR requires light pressing, while PAX Mini 2 and PAX Plus require strong packing. Arizer advises to lightly press the herb and leave 1-2 mm of free space.

Storz & Bickel and DynaVap state that a chamber that is packed too tightly or overfilled makes inhalation difficult; however, PAX for Mini 2 and Plus recommends strong packing. Storz & Bickel states this in the MIGHTY+ and CRAFTY+ instructions, as well as in VENTY and VEAZY. In the VENTY instructions, it adds that dosing capsules may restrict airflow. Topgreen recommends loosely filling the X-Max V3 Pro without overfilling.

DynaVap describes the compromise directly. A loosely packed M7 bowl allows more airflow. A tightly packed bowl provides more flavor, but inhalation becomes more difficult. For the Volcano Hybrid, the manufacturer only mentions the “desired amount” of herb, without describing packing.

Where do these differences come from? Manufacturers do not explain them. Therefore, when using a new device, start with what its instructions say, not from habits with previous equipment. Advice from one model may yield the opposite result in another.

If after filling the vaporizer the vapor is weak or inhalation is difficult, the guide vaporizer not producing vapor: what to check discusses the causes in order.

What Humidity is Appropriate for Herb?

The ASTM D8197-22 standard recommends a water activity (aw) of 0.55-0.65 for dried cannabis flowers. According to ASTM, aw below 0.65 protects against the growth of microorganisms such as mold. A value above 0.55 protects the herb from damage, meaning breaking. Similar thresholds are used in regulations in some US states.

All these thresholds apply to cannabis herb. Dried herbs, such as those in the herbs category, are not included.

Be careful with measures. Moisture content in percentage (e.g., mass loss after drying) and water activity are two different quantities. Oregon uses both, which is why it provides two separate thresholds. Do not convert one measure to another: 12% from the pharmacopoeia and 0.65 from the ASTM standard come from different measurements.

Drying also has its cost. A review by Gwinn et al. (Frontiers in Microbiology, 2023) states that drying lowers aw below 0.7, preventing the growth of most fungi. However, Eyal et al. (2023) write that terpene losses begin during drying and curing of the herb. If your herb is overdried, the guide how to moisturize overdried herb describes methods and common mistakes.

How to Store Herb to Preserve Aroma?

Best kept whole, in darkness and coolness, with limited air access. Fairbairn et al. (Journal of Pharmacy and Pharmacology, 1976) identified light as the largest single factor in cannabinoid loss. Air oxidation also caused significant losses. Temperature up to 20 °C had negligible impact in this study.

According to the same study, cannabis herb kept in darkness at room temperature was relatively stable for 1-2 years. Zamengo et al. (Forensic Science International, 2019) tracked samples for 4 years. In light and at room temperature, THC clearly decreased, while CBN increased. Temperature only changed the rate of these changes.

Milay et al. (Frontiers in Plant Science, 2020) compared several temperatures. They kept flowers in darkness at 25 °C, 4 °C, minus 30 °C, and minus 80 °C for a year. At 25 °C, cannabinoids changed the most: THCA content dropped by about 33% over the year. Terpenes decreased under all conditions, most at minus 80 °C. The authors considered storing whole flowers at 4 °C the best. Ground samples lost more terpenes than whole.

And what about humidity packs? The ASTM standard states that herb above 0.68 aw needs to be dried. Below this value, salt packs with a humidity of 0.55-0.65 can, according to ASTM, bring it to the recommended range. Boveda sells packs with relative humidity of 58% and 62%, both of which fall within the ASTM range. The manufacturer’s advice on which variant to choose is marketing material. We did not find studies to confirm it.

How to Recognize Mold on Herb and What to Do with It?

Do not use moldy herb, just dispose of it. This is recommended by Health Canada in a recall announcement for a batch of herb that exceeded limits for yeast, mold, and bacteria (April 2024). Consumers are to immediately stop using it and dispose of it in a way that prevents access to children. According to the agency, this batch may cause transient symptoms such as sneezing, coughing, wheezing, or itchy eyes, but serious effects are unlikely.

What does mold look like? A review by Gwinn et al. (2023) describes Penicillium spores visible on the surface of flowers. Botrytis causes browning and tissue death. Manufacturers destroy flowers with visible mold. We did not find a reliable home test, such as smell or UV light.

Does mold in herb harm? Benedict et al. (Emerging Infectious Diseases, CDC, 2020) analyzed data from insurance claims in the USA. Fungal infection occurred in 0.08% of cannabis users compared to 0.03% of non-users. After accounting for other factors, the odds were 3.5 times higher. This is a correlation, not proof of causation: the authors did not determine where the infections originated.

The risk mainly concerns individuals with reduced immunity. According to the 2023 review by Gwinn, cannabis is most often associated with Aspergillus fungi. Described cases of pulmonary aspergillosis concerned patients with reduced immunity after smoking cannabis. Heat should kill spores, but according to the review, it may not be enough to eliminate all. Ochratoxin A was detected in about 1/3 of 142 illegal samples, while it was absent in over 9,000 legal samples from California.

How Much Herb to Put in the Vaporizer for One Session?

As much as your device’s manufacturer specifies, and many manufacturers do not specify grams at all. DynaVap specifies 0.1 g for M7, and PAX about 0.3 g for FOUR. Storz & Bickel specifies for Volcano Hybrid a chamber of 6.5 cm³ and about 600 mg. All manufacturers’ numbers in one place:

• DynaVap The M7: 0.1 g.
• PAX FOUR: about 0.3 g.
• PAX Plus: lids for 0.25 g and 0.5 g.
• PAX Mini 2: 0.5 g when fully filled, 0.25 g when half (PAX press release).
• Volcano Hybrid: chamber 6.5 cm³, about 600 mg.

Storz & Bickel does not specify grams for its four portable devices (MIGHTY+, CRAFTY+, VENTY, VEAZY), although their chamber has a volume of 1.4 cm³. Arizer does not specify grams for Solo III and Air MAX. Topgreen is silent about grams for X-Max V3 Pro, and for Starry 4 only specifies a chamber of about 1.35 ml. For Fenix, we did not find the manufacturer’s data.

Can the chamber volume be converted to grams? The only pair of volume and mass is provided by Storz & Bickel for Volcano. This is data for one device, not a general conversion. We did not find a reliable conversion factor from cm³ to grams for other chambers. Therefore, do not calculate portions for a 1.4 cm³ chamber based on Volcano proportions. If the manufacturer does not specify grams, stick to its filling description from the table above.

After the session, the used herb, called ABV, remains, and what can be done with it is described in the guide how to use ABV herb.

Frequently Asked Questions

Do you need to grind herb for a vaporizer?

Usually yes, but the grind size depends on the device. Storz & Bickel and DynaVap prefer finer herb, Arizer coarsely ground, and PAX for FOUR medium-fine. Arizer also allows whole herb. We did not find any reviewed studies on particle size in vaporizers, so follow the instructions for your model.

Can you grind herb in advance?

It is better to grind just before the session. In the study by Milay et al. from 2020, all ground samples had fewer terpenes after storage than the whole flowers from which they came. Whole flowers also oxidized less. Therefore, store the herb whole and only grind the portion for the next session.

How many grams of herb fit in a vaporizer?

It depends on the model, and many manufacturers do not specify grams. DynaVap specifies 0.1 g for M7, PAX about 0.3 g for FOUR, and Storz & Bickel about 600 mg for the Volcano Hybrid chamber with a capacity of 6.5 cm³. Do not convert the volumes of other chambers to grams, as we did not find a reliable conversion factor.

What should be the humidity of cannabis herb?

The ASTM D8197-22 standard recommends a water activity of 0.55-0.65 for cannabis herb. The upper limit is to protect against mold, and the lower limit prevents the herb from breaking. The European Pharmacopoeia, according to the CI Council discussion, uses a different measure: a maximum of 12% mass loss after drying. Do not convert these two values to each other.

Does vaporization kill mold on herb?

It is not worth relying on this. A review by Gwinn et al. from 2023 states that heat should kill fungal spores, but it may not be enough to eliminate all of them. Health Canada, when recalling a batch of herb that exceeded limits for yeast, mold, and bacteria, recommended immediately stopping its use and disposing of it. Described cases of aspergillosis mainly concerned individuals with reduced immunity.

Can cannabis herb be kept in the fridge?

Yes, in the Milay 2020 study, the best composition was preserved in whole flowers kept in darkness at 4 °C. At 25 °C, THCA content dropped by about 33% over a year. Terpenes decreased under all conditions, most at minus 80 °C. According to Fairbairn (1976), the single largest factor in cannabinoid loss is light.

This article is for informational and educational purposes only and does not constitute medical advice. Before starting to use cannabis or CBD for therapeutic purposes, consult with a doctor, especially if you are taking other medications, are pregnant, or breastfeeding.

Author: Michał Waluk · Published: 2026-10-27 · Updated: 2026-10-27