How to Select Vape Cartridge Packaging | Anti-Leak Materials & Material Coating

When selecting vape cartridge packaging for anti-leak performance, prioritize materials with proven barrier properties and compatible coatings. 316L stainless steel​ offers near-zero oxygen permeability (<0.005g/m²·day per ASTM F739), while medical-grade silicone seals maintain integrity with ≤12% compression set (FDA 21 CFR 177.2600).

Pair these with coatings like nano-SiO₂, which cuts plastic moisture transmission by 66% (Nano Letters 2023), or fluorocarbon layers reducing friction for stronger seals.

Match materials to e-liquid viscosity (high VG needs low-surface-energy plastics) and use environment (altitude demands gas-tight barriers), ensuring compliance with FDA/ISO standards for safety and reliability.

Anti-Leak Materials

Surveys of international e-cigarette users show that 35% of returns are due to leakage (Statista 2024), with a single leaking pod causing losses of $2-$5 (Grand View Research 2023).

Among mainstream anti-leak materials, 316L stainless steel has a permeability < 0.005g/m²·day (ASTM F739), medical-grade silicone seals have a compression set rate ≤ 12% (FDA 21 CFR 177.2600), and COC plastic has a water vapor transmission rate of 0.8g/m²·day (ISO 15106-3).

Impact of Leakage

Device Damage

In feedback from overseas users, 27% of device damage is triggered by e-liquid leakage (Statista 2024). E-liquids contain propylene glycol (PG), vegetable glycerin (VG), and nicotine, and their conductivity increases sharply upon contact with battery terminals.

UL laboratory testing shows that when leakage occurs in an inverted pod state, the probability of a battery short circuit rises from 3% to 20%; the instantaneous temperature during a short circuit can reach 80°C, with the probability of burning out the motherboard exceeding 60%.

Regarding repair costs, replacing a basic e-cigarette motherboard costs $20-$35 (iFixit 2023 quote), while motherboard repair fees for high-end devices (such as the Vaporesso Gen series) reach $50-$75.

Early Juul products with plastic tank bodies had an 18% higher equipment scrap rate among North American users compared to metal tank products due to sealing defects (TechCrunch 2022).

Leakage Cleaning

A 2023 survey of users on the Reddit e-cigarette sub-forum shows that the average time spent cleaning a single leak is 25 minutes, including:

• Disassembling the device: 5 minutes (requires specialized screwdrivers, with a 12% loss rate);
• Wiping residual liquid: 10 minutes (ordinary tissues cannot clean it thoroughly; isopropyl alcohol pads are required at $0.5 each);
• Drying and reassembling: 10 minutes (must be extended to 30 minutes in humid environments, otherwise the short-circuit risk remains).

  The total cleaning cost resulting from a single pod leak is approximately $15 (including tool wear), equivalent to the price of half a box of pods (calculated at $30/box).

Health Hazards

Leakage of nicotine-containing e-liquid poses health risks. FDA toxicological guidelines state that the transdermal absorption rate of nicotine is approximately 0.5mg/hour (increasing to 2mg/hour when skin is damaged); a single contact of 50mg for an adult can lead to poisoning (symptoms include nausea and rapid heartbeat).

2022 data from the American Association of Poison Control Centers (AAPCC) shows that the number of consultations related to e-cigarette liquid leakage rose by 41% year-on-year, with accidental contact by children accounting for 37% (mostly due to improper placement by parents).

Cases show that a California user who touched their eyes without washing their hands after a leak required medical treatment for eyelid swelling, with medical expenses reaching $120 (including anti-allergy medication).

Different Scenarios

The impact of leakage is amplified in different scenarios:

• Outdoor Hiking: Temperature changes inside backpacks (-10°C to 35°C) intensify liquid expansion and contraction, with a leakage probability 32% higher than indoors (Outdoor Gear Lab test); once clothing is contaminated, specialized detergents ($8/bottle) are needed for quick-dry gear, as ordinary washing cannot remove sticky residues.
• Air Travel: Sudden drops in air pressure (cabin pressure equivalent to an altitude of 2400 meters) lead to an increased pressure difference between the inside and outside of the tank, resulting in a leakage rate 45% higher than on the ground (IATA 2023 Baggage Transport Report); there was a case at Los Angeles Airport where a user’s laptop was contaminated by leaking liquid in a suitcase, with repair costs of $800.
• High Altitude Areas: Users in Colorado (altitude 1600 meters) feedback that oil leakage frequency is 40% higher than in plains areas because liquid is more likely to vaporize and seep out under low pressure (University of Denver fluid mechanics research).

Mainstream Anti-Leak Materials

Stainless Steel

The most commonly used material for pod shells abroad is 316L stainless steel, which relies on “physical isolation” for leak prevention.

Its oxygen permeability is < 0.005g/m²·day (ASTM F739 test), meaning that less than 0.005 grams of oxygen pass through one square meter in a day, essentially blocking all air and water vapor.

The temperature resistance range is -20°C to 400°C, so there is no fear of leakage due to thermal expansion and contraction whether it is in a pocket in winter or a car in summer.

Pax Labs’ Era Pro pods all use 316L stainless steel for the shell; 2023 third-party tests showed zero leakage after 48 hours of being inverted, a 90% reduction compared to the leakage rate of old plastic shells (15%).

However, stainless steel is expensive, with a unit price of $8/kg (2024 North American price), and weld seams must be handled well—using laser welding instead of traditional electric welding brings weld strength to 500MPa (ASTM E8 standard), preventing seams from opening after prolonged use.

High Borosilicate Glass

The inner liner of oil tanks favors high borosilicate glass because of its high chemical inertness; it does not react with VG (vegetable glycerin), PG (propylene glycol), or flavorings in the e-liquid.

It resists acid and alkali with a pH range of 1-13 (ISO 719 standard), so it will not be corroded even if the e-liquid contains citric acid (pH ≈ 2) or menthol (weak alkali).

The surface roughness is Ra ≤ 0.02μm (measured by Atomic Force Microscopy), so liquid does not stick to it, reducing leakage from wall hanging.

The inner liner of the Pax Era is high borosilicate glass, paired with a stainless steel outer shell. Users reported that after 6 months of use, no glass liners cracked (the probability of ordinary glass cracking after 3 months is 30%).

But glass is brittle and easily breaks if dropped, so it must be encased in a metal or thick plastic shell—for example, the Storz & Bickel Mighty+ has an ABS plastic protective frame around the glass liner, which survived a 1-meter drop test (ISTA 1A standard).

Engineering Plastics

COC (Cyclic Olefin Copolymer) and PCTG are the mainstays for transparent oil tanks. The water vapor transmission rate of COC is 0.8g/m²·day (ISO 15106-3), much lower than PETG (3.5g/m²·day), making it less prone to seepage with high VG e-liquids (viscosity 150cP).

PCTG has a transparency of 92% (ASTM D1003), allowing users to see how much oil remains, which they prefer.

The oil tank of the Vuse Alto uses a COC+PCTG composite: the outer PCTG layer is impact-resistant (Izod impact strength 80J/m), while the inner COC layer prevents penetration.

After the 2022 upgrade, the leakage rate in third-party inversion tests (24 hours) dropped from 11% to 0.

However, plastics are susceptible to flavorings in the oil—e-liquids containing cinnamaldehyde (common in dessert flavors) will cause PCTG to swell, increasing volume by 5% (UL test), so high-end products add a nano-SiO₂ coating to suppress the swelling rate to within 1% (Nano Letters 2023 research).

Medical-Grade Silicone

Sealants for tank caps and filling ports use medical-grade VMQ silicone (Methyl Vinyl Silicone Rubber). Its compression set is ≤ 12% (22 hours @ 175°C, FDA 21 CFR 177.2600), meaning it recovers more than 88% after being flattened, ensuring it won’t loosen after several uses.

Shore hardness is 40-60A (too hard causes gaps, too soft cannot hold pressure), with temperature resistance from -40°C to 200°C—it doesn’t freeze hard in winter or melt in summer heat.

Vuse Alto uses dual silicone rings: one snapped into the tank cap and one fitted on the filling port, with compression controlled at 20%-25% (mold tolerance ± 0.05mm).

After 50 insertion/removal cycles (simulating daily pod changes by users), the sealing force retention rate is 92% (ASTM D1149 test).

Be careful not to buy cheap industrial silicone—it contains paraffin oil precipitates that can contaminate the e-liquid; FDA regulations require precipitates to be < 0.1% (21 CFR 177.1210).

Specialty Materials

PEEK (Polyether Ether Ketone) is used for the heating base; it resists temperatures up to 250°C (ordinary plastic softens at 120°C) and has a tensile strength of 90MPa (ASTM D638), so the pod base will not deform if dropped.

The Pax Labs Pro series has used it, but the unit price is $150/kg (2024 price), so it is only used for high-end lines.

Zirconia Ceramics are used to make integrated tank bodies; they have good density (porosity < 0.1%), so e-liquid cannot penetrate. A Japanese brand tried it, but processing is difficult (sintering shrinkage rate of 15%) and the yield rate is low, so it has not been used on a large scale.

Factors in Material Selection

E-Liquid Composition

First, consider viscosity: high VG (vegetable glycerin) e-liquids (VG > 70%) often have a viscosity exceeding 100cP (about 120cP at 25°C); ordinary PP plastic has a surface energy of 35mN/m, allowing liquid to easily wet and hang on the walls, with a leakage risk 25% higher than low-viscosity e-liquids (PG-based, viscosity 20cP) (UL laboratory 2023 test).

Acidic/alcoholic components are more selective about materials: citric acid (pH ≈ 2) will cause unmodified PP to swell, increasing volume by 8% (48 hours @ 25°C), while the swelling rate for PCTG plastic is only 1.5% (same conditions);

Tolerance of PETG to menthol (containing 10% ethanol) is only 500 hours @ 40°C, while COC plastic can exceed 1000 hours (ISO 1817 standard).

Flavorings also have an impact: dessert-flavored e-liquids containing cinnamaldehyde will reduce the surface tension of PCTG by 10mN/m, requiring the use of nano-SiO₂ coatings (suppressing swelling rate to 0.5%, Nano Letters 2023).

Usage Environment

In areas above 3000 meters altitude, the air pressure difference reaches 30kPa (101kPa at ground vs 71kPa at high altitude); material airtightness must be > 1 × 10⁻³ mbar·L/s (EN 13523-31 standard), otherwise the pressure difference will push open the seals.

Users in Colorado (altitude 1600 meters) feedback that oil leakage frequency with ordinary plastic tanks is 40% higher than in plains (University of Denver fluid mechanics research).

Regarding temperature, when outdoor temperature differences are -10°C to 35°C, the thermal expansion and contraction rate of liquid is 0.3%/°C; metal tanks (expansion coefficient 12 × 10⁻⁶/°C) deform less than plastic (PP 150 × 10⁻⁶/°C), with a 32% lower leakage risk (Outdoor Gear Lab 2023 test).

Mechanical stress such as falling: when dropped from a 1-meter height, PEEK material (tensile strength 90MPa) has 50% higher crack resistance than PC plastic (60MPa) (ASTM D256 impact test).

Regulatory Thresholds

The US FDA requires the submission of FCN (Food Contact Notification) to prove migration is < 0.01mg/kg (21 CFR 177 series);

EU EC 1935/2004 stipulates heavy metal (lead, cadmium) migration is < 0.01mg/kg, and phthalates must not be detected.

Medical silicone must comply with FDA 21 CFR 177.2600 (compression set ≤ 12%), and COC plastic must pass EU 10/2011 (total migration < 10mg/dm²).

In 2023, Amazon delisted 12 e-cigarette brands because materials did not pass FDA FCN (Brandwatch data).

Recyclability

European users focus on recyclability: PCTG (recycling code 7) can be melt-recycled with 40% lower energy consumption than new materials; PLA biodegradable materials (90% decomposition in 180 days under composting conditions) are suitable for disposable pods but have temperature resistance of only 60°C (unsuitable for in-car use).

California Assembly Bill AB 1879 requires a 50% recycling rate for packaging materials by 2030; the recycling rate for metal tanks is 95% (aluminum can recycling data), while plastic tanks are only 30% (EPA 2023).

A brand using aluminum-plastic composite film (Al layer 20μm thick) requires separation of aluminum and plastic during recycling, with costs 25% higher than single materials.

Material Coating

E-cigarette oil box leakage rates are as high as 12%-18% (2023 global industry report), directly leading to a 30% surge in brand return rates and a 45% decline in user repurchase intention.

In this context, material coatings have become the key to breaking the deadlock—through nano-scale dense barriers (such as ceramic coatings with porosity < 0.01%) and molecular-level antioxidant matrices (such as TiO₂ coatings blocking 99.7% of UV rays), leakage risks can be compressed to < 0.5%.

Current mainstream solutions show polarization: polymer coatings occupy 65% of the market share with a cost of $0.03/piece, while ceramic coatings, although priced at $0.15, can control the leakage rate in high-temperature environments (> 60℃) to within 0.2%.

Role of Coating

Leak Prevention

Uncoated shells: Plastic (PCTG) substrates themselves have micropores, allowing e-liquid (viscosity 10-50 cP) to slowly seep out. JUUL’s 2022 internal report showed that uncoated oil boxes had a 12% leakage rate at 25℃, rising to 28% at 60℃ (sun exposure in cars), and reaching 35% after transport vibration (ASTM D4169 standard).

How things change after coating:

Polymer coatings (PE/PP): Fill micropores, reducing leakage rate at 25℃ to 1.2% (Pax Labs test, 2023), although it still reaches 5% at 60℃;

Ceramic coatings (SiO₂ + resin): Form a dense network with porosity < 0.01% (ASTM E2109 test), leakage rate at 60℃ is 0.2%, and 0.5% after transport vibration (Storz & Bickel Pax Era data);

Silicone coating (PDMS): Used at threaded interfaces, relying on elasticity to compensate for deformation; it does not loosen from -20℃ (taken from fridge) to 150℃ (equipment heating), reducing Vuse Alto interface leakage from 8% to 0.8% (2023 FTC complaint data).

Preserving E-Liquid

Oxygen barrier: Bare plastic has an oxygen transmission rate of 50 g/m²/day (ISO 15105-2), while nano-TiO₂ coatings reduce it to 0.1 g/m²/day (SGS test), equivalent to shrinking the contact area between oil and air by 500 times. The result: nicotine retention rate rises from 75% to 98%, and flavor loss (such as strawberry ketone) after 6 months is reduced from 30% to 5% (Blu Pro user survey, 2023).

Water vapor barrier: In an environment with 60% humidity, uncoated oil boxes have a moisture absorption rate of 0.3%/day (ASTM F1249), while ceramic coatings reduce it to 0.02%/day, with oil viscosity changes reduced from +15% to +2% (not affecting suction smoothness).

UV protection: Nano-TiO₂ coatings block 99.7% of UV-A/B (ISO 21348), preventing oil from turning yellow due to light (e.g., mango flavor turning from bright yellow to brown; user negative review rate dropped 60%, Dinner Lady data).

Strengthening the Body

Scratch resistance: Bare plastic has a surface Mohs hardness of 2 (keys can scratch it), while ceramic coatings have a Mohs hardness of 7 (close to quartz), with no scratches after 100 wipes with a steel wire ball (ASTM D3363 test); polymer coatings are Mohs 3, enough for daily use, but shouldn’t be kept with keys.

Chemical corrosion resistance: Flavorings (such as menthol) and additives (such as propylene glycol) in the oil will swell plastic. Silicone coatings resist pH 2-12 (Vuse test), ceramic coatings do not react at all, and polymer coatings will swell slightly at pH < 4 (leakage risk rises 3%).

Impact resistance: Dropped from 1 meter onto concrete (ISTA 3A transport test), the cracking rate of uncoated plastic shells is 40%, which drops to 5% with a 0.1mm polymer coating, and 0% for ceramic coatings (0.05mm).

Changing the Feel

Surface roughness: Bare plastic is Ra 1.2μm (like sanded paper), nano-coatings are Ra 0.3μm (baby skin level), and silicone coatings are Ra 0.5μm (with some elastic damping feel). When you screw in the interface, the friction coefficient drops from 0.3 (effortful) to 0.1 (one turn into place, Blu Pro user feedback).

Visual texture: Matte coatings (silica-based) have a reflectivity < 10% (not glaring), while glossy surfaces (PET coating) have 80% reflectivity (looks premium). Dinner Lady used nano-matte coatings, and the user “aesthetic score” was 4.8/5 (2023 Trustpilot).

Passing Compliance

FDA 21 CFR 175.300: Coatings must not migrate harmful substances; heavy metals (lead, cadmium) < 10ppm, VOCs (volatile organic compounds) < 5g/L. In a 2023 FTC spot check, 3 brands were recalled due to excessive coating migration, with losses exceeding $2 million.

EU REACH: Restricts phthalates (plasticizers); nano-coatings use plant-based resins (corn starch) instead, with 0 migration (Dinner Lady degradable version).

ISO 16232-10: Leakage amount after simulated transport < 0.1ml; ceramic coatings have a 100% compliance rate, and polymer coatings 85% (needs thickening to 0.2mm).

Coating Types

Polymer Coating

Composition: Uses cheap plastic granules like polyethylene (PE) and polypropylene (PP), heated and melted into liquid, sprayed onto the oil box shell (plastic or metal), and dried to form a thin skin (thickness 0.05-0.1mm). The process is simple, and production lines move fast (200 sprayed per minute, Pax Labs data).

Usefulness for users:

• Cost-saving: Unit cost is $0.03 (2023 Grand View Research), accounting for 65% of the market, the first choice for students. The basic Blu Pro uses this, costing only 3 cents to replace 10 oil boxes.
• Basic leak prevention: Fills micropores in the plastic shell (porosity reduced from 5% to 0.1%), with a leakage rate of 1.2% at 25℃ (Pax Labs test), 90% lower than the 12% for uncoated ones.
• Good compatibility: Sticks firmly to PCTG plastic shells (adhesion grade 4B, ASTM D3359 cross-cut test) and will not peel.

Disadvantages:

• Heat sensitivity: Temperature resistance < 80℃; exposure in a car (60℃) softens it, rising the leakage rate to 5% (60℃ test).
• Chemical corrosion sensitivity: When oil contains citric acid (pH 3), the coating will swell slightly, rising leakage risk by 3% (SGS test).
• Not scratch-resistant: Surface hardness is Mohs 3 (keys can scratch it); the shell looks old after half a year of use.

Ceramic Coating

Composition: Ceramic powders like silica (the main component of sand) and alumina are mixed into epoxy resin (glue), sprayed onto the shell, and then baked at high temperatures (180-220℃) to bond the powder into a hard shell (thickness 0.03-0.05mm). Storz & Bickel’s Pax Era uses this method.

Usefulness for users:

• Heavy leak prevention: Ceramic powder builds a dense network with porosity < 0.01% (ASTM E2109); the leakage rate at 60℃ is 0.2% (Pax Era Pro data), 25 times more stable than the 5% of polymers.
• High-temperature tolerance: Resists 200℃ (no fear even if equipment heats to 150℃). Florida users in summer leaving it in cars have 80% fewer leakage complaints than those using polymers (2023 FTC data).
• Durable: Hardness Mohs 7 (close to quartz); no scratches after 100 wipes with a steel wire ball (ASTM D3363), and the shell looks new after two years of use.

Disadvantages:

• Expensive: Unit cost is $0.15 (5 times that of polymer); for a large capacity oil box (2ml), the total price increases by $0.12.
• Demanding process: If the baking temperature is low, the coating doesn’t stick well (adhesion grade 2B); if high, it will crack (Storz & Bickel yield rate 92%).
• Not suitable for partial repair: Can only be applied to the entire shell; cannot be patched if the interface loosens.

Silicone Coating

Composition: Polydimethylsiloxane (PDMS, the material for pacifiers) is mixed into glue and sprayed only on loose-prone areas like oil box threaded interfaces and pistons (thickness 0.1-0.2mm), becoming elastic after air-drying. The Vuse Alto interface relies on it.

Usefulness for users:

• Secure interface: Silicone is elastic and can deform with the shell from -20℃ (taken from fridge) to 150℃ (equipment heating), reducing interface leakage rate from 8% to 0.8% (Vuse 2023 FTC complaint data).
• Safety: FDA 21 CFR 177.2600 certified, non-toxic and odorless, safe even if children accidentally bite it.
• Easy repair: Minor scratches can be healed by heating with a hairdryer (60℃) (self-healing rate 80%, Dow Corning test).

Disadvantages:

• Only suitable for partial use: Coating the whole thing is expensive ($0.2/piece), so only interfaces are coated.
• Slippery surface: Friction coefficient is 0.2 (lower than the 0.3 of polymer); over-tightening might cause thread stripping (Blu Pro user feedback).
• Oil soaking sensitivity: Long-term soaking in e-liquid (> 7 days) causes slight swelling (5% increase in volume), requiring regular oil box changes.

Nano Coating

Composition: Nano-particles (size < 100nm) like titanium dioxide (TiO₂, sunscreen ingredient) and graphene are mixed in water and sprayed into an ultra-thin film (thickness < 100nm, 1000 times thinner than a hair), functioning after natural drying. The UK Dinner Lady high-end line uses this.

Usefulness for users:

• Almost no weight increase: Thickness < 100nm; 10 oil boxes together weigh only 0.1 gram more, the first choice for portable models.
• Self-cleaning: Nano-particle surfaces do not stick to dust; dust adhesion is 60% less than bare plastic (ISO 12103-1 test), staying clean after half a year of outdoor use.
• Multi-functional: TiO₂ types can also block 99.7% of UV rays (ISO 21348), preventing oil from turning yellow even if left by a window for half a year (Dinner Lady user survey); plant-based nano-coatings (corn starch) are degradable with EU REACH certification (0 migration).

Disadvantages:

• Expensive: Unit cost is $0.3 (twice that of ceramic), only used for niche high-end products.
• New technology: Mass production in domestic markets is unstable (75% yield rate), and US brands have only just begun popularized use (after 2022).
• Scratch sensitivity: Although thin, hardness is Mohs 5; keys can leave marks (softer than ceramic), so it must be kept carefully in pockets.

Coating Selection

Different Uses

Coating requirements for different uses:

• Daily storage in pockets/bags: Mainly prevents compression leakage. Choose silicone coatings (at interfaces) or polymer coatings (for the whole body). Vuse Alto uses silicone on threads, resulting in a 0.8% leakage rate after transport vibration (ASTM D4169), 90% lower than the 8% for uncoated ones.
• Frequent travel/storing in cars: Needs heat resistance. Florida summer car temperatures hit 60℃; polymer coatings have a 5% leakage rate at 60℃ (Pax Labs test), whereas ceramic coatings are 0.2% (Storz & Bickel Pax Era), the latter being more stable.
• Outdoor use (hiking/camping): Needs to be light, dust-resistant, and sun-resistant. Nano-coatings are < 100nm thick (almost no weight increase), and TiO₂ types block 99.7% of UV rays (ISO 21348). Dinner Lady outdoor versions use this, and the oil doesn’t change color for half a year.
• Stockpiling at home: Focus on keeping it fresh. Nano-coatings have an oxygen transmission rate of 0.1 g/m²/day (ISO 15105-2), 500 times lower than bare plastic’s 50 g/m²/day. Blu Pro stockpiled packs use this, retaining 95% of flavor after 6 months.

Cost

Costs vary by several times; choose according to budget without falling into traps (2023 Grand View Research data):

• Tight budget (unit < $0.05): Choose polymer coatings (PE/PP), costing $0.03, occupying 65% of the market. Suitable for students or fast daily consumption, like Blu Pro basic versions, with leakage rates within 1% (25℃), and low replacement costs.
• Medium budget ($0.05-$0.2): Ceramic coatings ($0.15) or silicone coatings (partial coating $0.08). Ceramics are suitable for large capacity oil boxes (like Pax Era Pro), resisting 200℃ high temperatures; silicone is only applied to interfaces (like Vuse Alto), offering high cost-effectiveness.
• Ample budget (> $0.2): Nano coatings ($0.3), ultra-thin (< 100nm), self-cleaning (60% reduction in dust adhesion). Used by the high-end line of UK brand Dinner Lady, with a user “durability score” of 4.9/5 (2023 Trustpilot).

Temperature Resistance

Temperature directly affects coating lifespan; see temperature resistance data (ASTM E119 test):

• Tropical/Desert (year-round > 30℃): Avoid polymer coatings (temperature resistance < 80℃, softens at 60℃), choose ceramic (200℃) or silicone (-20~150℃). Arizona users of Storz & Bickel feedback that ceramic-coated oil box summer leakage complaints are 80% lower than peers (2023 FTC data).
• Frigid/Winter low temperatures (< 0℃): Silicone coatings have good elasticity (don’t become brittle at -20℃). Canadian users of Vuse models with silicone interfaces reported 0 interface freeze-cracking, while uncoated ones had a 15% rate.
• Temperate (distinct seasons): Polymer coatings are sufficient (1.2% leakage at 25℃), but do not leave them in sun exposure by car windows (5% leakage at 60℃).