E-cigs vs. T-cigs
Electronic cigarettes may be less harmful in the UK than cigarettes but may still be dangerous. Under which circumstances should a person use ecigs? Will they fill your body with plastic?
Electronic cigarettes can contain propylene glycol or vegetable glycerine with nicotine (and in at least two cases polyethylene glycol 400) to form a solution that when heated by an atomizer, produces a visible vapour that provides nicotine to the bloodstream via the lungs when inhaled.
Electronic cigarettes have not been studied enough by scientists in laboratories to form conclusive evidence that their use is either beneficial or harmful to humans. However, some are concerned that unknown side-effects could occur with continuous, consistent use of electronic cigarettes, including cancer.
Behaviour surrounding their use is worrisome because e-cigs are being used habitually by a percentage of non-smokers who otherwise would not use nicotine, they may seem attractive to children, they are not closely regulated, and their use makes it very easy to overdose on nicotine even for experienced smokers.
UK Electronic Cigarettes and E-Liquid(Redirected from E-liquid) Aerosol (vapor) exhaled by an e-cigarette user.
The aerosol of electronic cigarettes is generated when the e-liquid reaches a temperature of roughly 100–250 °C within a chamber. The user inhales the aerosol, commonly called vapor, rather than cigarette smoke. The aerosol provides a flavor and feel similar to tobacco smoking. In physics, a vapor is a substance in the gas phase whereas an aerosol is a suspension of tiny particles of liquid, solid or both within a gas. Vapor from an electronic cigarette simulates tobacco smoke, but the process of burning tobacco does not occur. The aerosol is made-up of liquid sub-micron particles of condensed vapor, which mostly consist of propylene glycol, glycerol, water, flavorings, nicotine, and other chemicals. The various chemicals in the aerosol give rise to many issues concerning the safety of electronic cigarettes that have been much discussed. After a puff, inhalation of the aerosol travels from the device into the mouth and lungs. A 2014 review found that the particles emitted by e-cigarettes are comparable in size and number to particles in cigarette smoke, with the majority of them in the ultrafine range. The particles are of the ultrafine size which can go deep in the lungs and then into the systemic circulation. A 2014 review said local pulmonary toxicity may occur because metal nanoparticles can deposit in the lungs. Others show that the quantities of metals emitted are minimal and permissible by medicinal standards.Various bottles of e-liquid.
After the aerosol is inhaled, it is exhaled. Emissions from electronic cigarettes are not comparable to environmental pollution or cigarette smoke as their nature and chemical composition are completely different. The particles are larger, with the mean size being 600 nm in inhaled aerosol and 300 nm in exhaled vapor. Bystanders are exposed to these particles from exhaled e-cigarette vapor. There is a concern that some of the mainstream vapor exhaled by e-cigarette users can be inhaled by bystanders, particularly indoors, and have significant adverse effects. Since e-cigarettes involve an aerosolization process, it is suggested that no meaningful amounts of carbon monoxide are emitted. Thus, cardiocirculatory effects caused by carbon monoxide are not likely. E-cigarette use by an expectant parent might lead to inadvertent health risks to offspring. E-cigarettes pose many safety concerns to children. For example, indoor surfaces can accumulate nicotine where e-cigarettes were used, which may be inhaled by children, particularly youngsters, long after they were used.
E-liquid is the mixture used in vapor products such as electronic cigarettes. The main ingredients in the e-liquid usually are propylene glycol, glycerin, nicotine, and flavorings. However, there are e-liquids sold without propylene glycol, nicotine, or flavors. The liquid typically contains 95% propylene glycol and glycerin. Propylene glycol and glycerine are used to produce the vapor while the flavoring provides the taste and aroma. The flavorings may be natural or artificial. About 8,000 flavors exist as of 2014. There are many e-liquids manufacturers in the USA and worldwide. While there are currently no US Food and Drug Administration (FDA) manufacturing standards for e-liquid, the FDA has proposed regulations that were expected to be finalized in late 2015. Industry standards have been created and published by the American E-liquid Manufacturing Standards Association (AEMSA).
The vapor can contain nicotine and usually contains vegetable glycerin, propylene glycol, flavors and aroma transporters. The nicotine levels in the vapor varies either from puff-to-puff or among products of the same company. A 2015 report commissioned by Public Health England concluded that e-cigarettes "release negligible levels of nicotine into ambient air". E-cigarettes without nicotine are also available. The vapor may also contain tiny amounts of toxicants, carcinogens, and heavy metals. Contamination with various chemicals has been identified. E-cigarette makers do not fully disclose information on the chemicals that can be released or synthesized during use. The metals have been found in trace amounts in the vapor, some of them at higher amounts than in cigarette smoke. The peak concentration of nicotine delivered by e-cigarette use is comparable to that produced by conventional cigarette smoking.An example of a commercial e-liquid and an advanced personal vaporizer.
E-liquid, e-fluid, or e-juice is the mixture used in vapor products including e-cigarettes. E-Liquids come in many variations, including different nicotine strengths and many different flavors. The main ingredients are propylene glycol, glycerine, and flavorings; and most often, nicotine in liquid form. The liquid typically contains 95% propylene glycol and glycerin, and the remaining 5% being flavorings and nicotine. E-liquid can be made with or without nicotine, with >90% of e-liquids containing some level of nicotine. The most regularly used base carrier chemical is propylene glycol with or without glycerin. E-liquid containing glycerin and water made without propylene glycol are also sold. Unless clearly stated, it is uncertain whether the nicotine used in e-liquid is manufactured using a United States Pharmacopeia (USP) grade nicotine, a tobacco plant extract, tobacco dust or a synthetic nicotine. Most e-cigarette liquids contain nicotine, but the level of nicotine varies depending on user-preference and manufacturers. Although some e-juice is nicotine-free, surveys demonstrate that 97% of responders use products that contain nicotine. A 2015 review suggests that 1% of users use liquid without nicotine.
The primary parts that make up an e-cigarette are a mouthpiece, a cartridge (tank), a heating element/atomizer, a microprocessor, a battery, and possibly a LED light on the end. An atomizer comprises a small heating element that vaporizes e-liquid and wicking material that draws liquid onto the coil. When the user pushes a button. or inhales a pressure sensor activates the heating element that atomizes the liquid solution; The e-liquid reaches a temperature of roughly 100–250 °C within a chamber to create an aerosolized vapor. The user inhales the aerosol, commonly called vapor, rather than cigarette smoke. The aerosol provides a flavor and feel similar to tobacco smoking. However, variable voltage devices can raise the temperature where the user adjusts the vapor. The vapor contains similar chemicals to the e-liquid which vary in composition and concentration across and within manufacturers.
E-cigarettes produce particles, in the form of an aerosol. In physics, a vapor is a substance in the gas phase whereas an aerosol is a suspension of tiny particles of liquid, solid or both within a gas. The aerosol is made-up of liquid sub-micron particles of condensed vapor, which mostly consist of propylene glycol, glycerol, water, flavorings, nicotine, and other chemicals. This aerosol that is produces resembles cigarette smoke. After a puff, inhalation of the aerosol travels from the device into the mouth and lungs.
A 2014 review found that the particles emitted by e-cigarettes are comparable in size and number to particles in cigarette smoke, with the majority of them in the ultrafine range. The ultrafine particles can go deep in the lungs and then into the systemic circulation. Pulmonary toxicity may occur because metal nanoparticles can deposit in the lungs. The review also found that fine particles can be chemically intricate and not uniform, and what a particle is made of, the exact harmful elements, and the importance of the size of the particle is mostly unknown. They found that because these things are uncertain, it is not clear whether the ultrafine particles in e-cigarette vapor have health effects similar to those produced by traditional cigarettes.
A 2014 WHO report found e-cigarettes release a lower level of particles than traditional cigarettes. Comparable to a traditional cigarette, e-cigarette particles are tiny enough to enter the alveoli, enabling nicotine absorption. E-cigarettes companies assert that the particulates produced by an e-cigarette are too tiny to be deposited in the alveoli. Exactly what comprises the vapor varies in composition and concentration across and within manufacturers. Different devices generate different particle sizes and cause different depositions in the respiratory tract, even from the same nicotine liquid. Reports in the literature have shown respiratory and cardiovascular effects by these smaller size particles, suggesting a possible health concern.
After the aerosol is inhaled, it is exhaled. Emissions from electronic cigarettes are not comparable to environmental pollution or cigarette smoke as their nature and chemical composition are completely different. The particles are larger, with the mean size being 600 nm in inhaled aerosol and 300 nm in exhaled vapor. The exhaled aerosol particle concentration is 5 times lower from an e-cigarette than from a combustible tobacco cigarette. The density of particles in the vapor is lower than in cigarette smoke by a factor of between 6 and 880 times lower.
For particulate matter emissions, e-cigarettes slightly exceeded the WHO guidelines, but emissions were 15 times less than traditional cigarette use. In January 2014, the International Union Against Tuberculosis and Lung Disease stated "Adverse health effects for exposed third parties (second-hand exposure) cannot be excluded because the use of electronic cigarettes leads to emission of fine and ultrafine inhalable liquid particles, nicotine and cancer-causing substances into indoor air." The dense vapor consists of liquid sub-micron droplets.[dead link]
Since e-cigarettes have not been widely used long enough for evaluation, the long-term health effects from the second-hand vapor are not known. There is insufficient data to determine the impact on public health from e-cigarettes. The potential harm to bystanders from e-cigarettes is unknown. This is because no long-term data is available.
Since e-cigarettes do not burn (or contain) tobacco, no side-stream smoke or any cigarette smoke is produced. Only what is exhaled by e-cigarettes users enters the surrounding air. Exhaled vapor consists of nicotine and some other particles, primarily consisting of flavors, aroma transporters, glycerin and propylene glycol. Bystanders are exposed to these particles from exhaled e-cigarette vapor. A mixture of harmful substances, particularly nicotine, ultrafine particles, and volatile organic compounds can be exhaled into the air. The liquid particles condenses into a viewable fog. The vapor is in the air for a short time, with a half-life of about 10 seconds; traditional cigarette smoke is in the air 100 times longer. This is because of fast revaporization at room temperature.
There is a concern that some of the mainstream vapor exhaled by e-cigarette users can be inhaled by bystanders, particularly indoors, and have significant adverse effects. Since e-cigarettes involve an aerosolization process, it is suggested that no meaningful amounts of carbon monoxide are emitted. Thus, cardiocirculatory effects caused by carbon monoxide are not likely. However, in an experimental study, e-cigarettes increased levels of carcinogenic polycyclic aromatic hydrocarbons in the surrounding air.
E-cigarettes used in indoor environments can put at risk nonsmokers to elevated levels of nicotine and aerosol emissions. Nonsmokers exposed to e-cigarette aerosol produced by a machine and pumped into a room were found to have detectable levels of the nicotine metabolite cotinine in their blood. The same study stated that 80% of nicotine is normally absorbed by the user, so these results may be higher than in actual second hand exposure. In 2015 a report commissioned by Public Health England concluded that e-cigarettes "release negligible levels of nicotine into ambient air with no identified health risks to bystanders".
A 2014 review of limited data concluded this vapor can cause indoor air pollution and is not just water vapor as is frequently stated in the advertising of e-cigarettes. A 2014 practice guideline by NPS MedicineWise states, "Although data on health effects of passive vapour are currently lacking, the risks are argued to be small, but claims that e-cigarettes emit only water vapour are nevertheless incorrect. Serum cotinine levels (a metabolite of nicotine) have been found to be similar in bystanders exposed to either e-cigarette vapour or cigarette smoke." The 2015 California Department of Public Health has reported that "Mainstream and second hand e-cigarette aerosol has been found to contain at least ten chemicals that are on California's Proposition 65 list of chemicals known to cause cancer, birth defects, or other reproductive harm." However, it has been demonstrated that e-cigarettes causes nonusers to be exposed to nicotine but not to tobacco-related combustion toxicants.A no smoking or vaping sign from the US.
A white paper published in 2014 by the American Industrial Hygiene Association concluded e-cigarettes emit airborne contaminants that may be inhaled by the user and those nearby. They urged indoors restrictions similar to smoking bans, until research has shown the aerosol has no risk of harm. A 2014 review indicated that the levels of inhaled contaminants from the e-cigarette vapor are not of significant health concern for human exposures by the standards used in workplaces to ensure safety. The use of e-cigarettes in a smoke-free area could expose non-users to toxins. The effect on bystanders would likely be much less harmful than traditional cigarettes.
2014 WHO report stated passive exposure was as a concern, indicating that current evidence is insufficient to determine whether the levels of exhaled vapor are safe to involuntarily exposed bystanders. The report stated that "it is unknown if the increased exposure to toxicants and particles in exhaled aerosol will lead to an increased risk of disease and death among bystanders." The British Medical Association (BMA) reported in 2013 that there are "concerns that the use of e-cigarettes could threaten the norm of not smoking in public places and workplaces."
As of 2013[update], the only clinical study currently published evaluating the respiratory effects of passive vaping found no adverse effects were detected. A 2014 review found it is safe to infer that their effects on bystanders are minimal in comparison to traditional cigarettes. A E-cigarette vapor has notably fewer toxicants than cigarette smoke and is likely to pose less harm to users or bystanders.
E-cigarette use by a parent might lead to inadvertent health risks to offspring. E-cigarettes pose many safety concerns to children. For example, indoor surfaces can accumulate nicotine where e-cigarettes were used, which may be inhaled by children, particularly youngsters, long after they were used. A policy statement by the American Association for Cancer Research and the American Society of Clinical Oncology has reported that "Third-hand exposure occurs when nicotine and other chemicals from second-hand aerosol deposit on surfaces, exposing people through touch, ingestion, and inhalation". Public health England, looking at the available research said the amount of nicotine deposited was low and that an infant would have to lick 30 square meters to be exposed to 1 mg of nicotine. The statement noted there are no published studies of third hand exposure from e-cigarettes, however initial data suggests that nicotine from e-cigarettes may stick to surfaces and would be hard to remove.
The e-liquid is sold in bottles or pre-filled disposable cartridges, or as a kit for consumers to make their own e-juices. Some vendors of e-liquids, offer options to change the amounts of flavorings or nicotine strengths, and build each bottle customized for the purchaser. E-liquids are made with various tobacco, fruit, and other flavors, as well as variable nicotine concentrations (including nicotine-free versions). The standard notation "mg/ml" is often used on labels to denote nicotine concentration, and is sometimes shortened to "mg". In surveys of regular e-cigarette users, the most popular e-liquids have a nicotine content of 18 mg/ml, and the preferred flavors were largely tobacco, mint and fruit. A cartridge may contain 0 to 20 mg of nicotine. EU regulations cap the concentration of nicotine in e-liquid at a maximum of 20 mg/mL. A refill bottle can contain up to 1 g of nicotine. Refill liquids are often sold in the size range from 15 to 30 mL. One cartridge may typically last as long as one pack of cigarettes. Some liquids without flavoring is also sold. The flavorings may be natural or artificial. There is even certified organic liquid. About 8,000 flavors exist as of 2014. A user does not normally consume a whole cartridge in a single session. Most e-liquids are produced by a few manufacturers in China, the US and Europe. An e-cigarette user will usually obtain 300 to 500 puffs per mL of liquid.
The two most common e-liquid bases are propylene glycol (PG) and vegetable glycerin (VG). Propylene glycol is tasteless and odorless, and therefore it doesn't affect the flavor of the e-liquid. It is known, however, to cause allergic reactions in some users, and in such case it is advised to stop the use immediately. Vegetable glycerin, on the other hand, is a lot thicker in consistency, and it doesn't cause allergic reactions. It also produces significantly more vapor, which has a slight sweet taste.[unreliable source?]
E-liquids are manufactured by many producers, both in the US and across the world. First tier manufacturers use lab suits, gloves, hair covers, inside of certified clean rooms with air filtration similar to pharmaceutical-grade production areas.
Standards for e-liquid manufacturing have been created by American E-liquid Manufacturing Standards Association (AEMSA), which is trade association dedicated to creating responsible and sustainable standards for the safe manufacturing of e-liquids used in vapor products. AEMSA has published a comprehensive list standards and best known methods, which are openly available for use by any manufacturer of e-Liquids. The AEMSA standards cover nicotine, ingredients, sanitary manufacturing rooms, safety packaging, age restrictions, and labeling.
There are no current governmental or US Food and Drug Administration (FDA) manufacturing standards for e-liquid. The FDA has sought to regulate e-liquid through use of the Tobacco Control Act, passed into law in 2009. In April 2014, the FDA issued its "Deeming" proposals for public comment, which would cover e-liquids manufacturing. The Final Rule, (in final form) giving the FDA authority to regulate e-liquids was released on May 5th 2016.
2017 Beyond the Data -- E-cigarettes: An Emerging Public Health Challenge UK
Disassembled parts of a first generation e-cigarette. A. LED light cover B. battery (also houses circuitry) C. atomizer (heating element) D. cartridge (mouthpiece) Parts of a second generation e-cigarette. An electronic cigarette is a battery-powered vaporizer. The primary parts that make up an e-cigarette are a mouthpiece, a cartridge (tank), a heating element/atomizer, a microprocessor, a battery, and possibly a LED light on the end. An atomizer comprises a small heating element that vaporizes e-liquid and wicking material that draws liquid onto the coil. When the user pushes a button, or (in some variations) activates a pressure sensor by inhaling, the heating element then atomizes the liquid solution The e-liquid reaches a temperature of roughly 100-250 °C within a chamber to create an aerosolized vapor. The user inhales the aerosol, commonly called vapor, rather than cigarette smoke. The aerosol provides a flavor and feel similar to tobacco smoking. There are three main types of e-cigarettes: cigalikes, looking like cigarettes; eGos, bigger than cigalikes with refillable liquid tanks; and mods, assembled from basic parts or by altering existing products. As the e-cigarette industry continues to evolve, new products are quickly developed and brought to market. First generation e-cigarettes tend to look like tobacco cigarettes and so are called "cigalikes". Most cigalikes look like cigarettes but there is some variation in size. Second generation devices are larger overall and look less like tobacco cigarettes. Third generation devices include mechanical mods and variable voltage devices. The fourth generation includes Sub ohm tanks and temperature control devices. The power source is the biggest component of an e-cigarette, which is frequently a rechargeable lithium-ion battery. A later-generation box mod e-cigarette. Image courtesy of Ecigclick An e-cigarette is a handheld battery-powered vaporizer that simulates smoking, but without tobacco combustion. Once the user inhales, the airflow activates the pressure sensor, and then the heating element atomizes the liquid solution. Most devices have a manual push-button switch to turn them on or off. E-cigarettes do not turn on by trying to "light" the device with a flame. The e-liquid reaches a temperature of roughly 100-250 °C within a chamber to create an aerosolized vapor. However, variable voltage devices can raise the temperature. A glycerin-only liquid vaporizes at a higher temperature than a propylene glycol-glycerin liquid. Rather than cigarette smoke, the user inhales an aerosol, commonly but inaccurately called vapor. E-cigarettes do not create vapor between puffs. Vaping is different than tobacco smoking, but there are some similarities with their behavioral habits, including the hand-to-mouth action and a vapor that looks like cigarette smoke. E-cigarettes provide a flavor and feel similar to smoking. A noticeable difference between the traditional cigarette and the e-cigarette is sense of touch. A traditional cigarette is smooth and light but an e-cigarette is rigid, cold and slightly heavier. Since e-cigarettes are more complex than traditional cigarettes, a learning curve is needed to use them correctly. Compared to traditional cigarettes, the general e-cigarette puff time is much longer, and requires a more forceful suction than a regular cigarette. The volume of vapor created by e-cigarette devices in 2012 declined with vaping. Thus, to create the same volume of vapor increasing puff force is needed. Later-generation e-cigarettes with concentrated nicotine liquids may deliver nicotine at levels similar to traditional cigarettes. Many e-cigarette versions include a voltage potentiometer to adjust the volume of vapor created. The amount of vapor produced is controlled by the power from the battery, which has led some users to adjust their devices to increase battery power. An ordinary cigarette compared to a "cigalike" e-cigarette E-cigarettes are usually approximately cylindrical, with many variations: pen-styles, tank-styles etc. Some e-cigarettes look like traditional cigarettes, but others do not. There are three main types of e-cigarettes: cigalikes, looking like cigarettes; eGos, bigger than cigalikes with refillable liquid tanks; and mods, assembled from basic parts or by altering existing products. The primary parts that make up an e-cigarette are a mouthpiece, a cartridge (tank), a heating element/atomizer, a microprocessor, a battery, and possibly a LED light on the end. The only exception to this are mechanical e-cigarettes (mods) which contain no electronics and the circuit is closed by using a mechanical action switch. E-cigarettes are sold in disposable or reusable variants. Disposable e-cigarettes are discarded once the liquid in the cartridge is used up, while rechargeable e-cigarettes may be used indefinitely. A disposable e-cigarette lasts to around 400 puffs. Reusable e-cigarettes are refilled by hand or exchanged for pre-filled cartridges, and general cleaning is required. A wide range of disposable and reusable e-cigarettes exist. Disposable e-cigarettes are offered for a few dollars, and higher-priced reusable e-cigarettes involve an up-front investment for a starter kit. Some e-cigarettes have a LED at the tip to resemble the glow of burning tobacco. The LED may also indicate the battery status. The LED is not generally used in personal vaporizers or mods. First-generation e-cigarettes usually simulated smoking implements, such as cigarettes or cigars, in their use and appearance. Later-generation e-cigarettes often called mods, PVs (personal vaporizer) or APVs (advanced personal vaporizer) have an increased nicotine-dispersal performance, house higher capacity batteries, and come in various shapes such as metal tubes and boxes. They contain silver, steel, metals, ceramics, plastics, fibers, aluminum, rubber and spume, and lithium batteries. A growing subclass of vapers called cloud-chasers configure their atomizers to produce large amounts of vapor by using low-resistance heating coils. This practice is known as cloud-chasing. Many e-cigarettes are made of standardized replaceable parts that are interchangeable between brands. A wide array of component combinations exists. Many e-cigarettes are sold with a USB charger. E-cigarettes that resemble pens or USB memory sticks are also sold for those who may want to use the device unobtrusively. As the e-cigarette industry continues to evolve, new products are quickly developed and brought to market. Various types of e-cigarettes. First-generation e-cigarettes tend to look like tobacco cigarettes and so are called "cigalikes". The three parts of a cigalike e-cigarette initially were a cartridge, an atomizer, and a battery. A cigalike e-cigarette currently contains a cartomizer (cartridge atomizer), which is connected to a battery. Most cigalikes look like cigarettes but there is some variation in size. They may be a single unit comprising a battery, coil and filling saturated with e-juice in a single tube to be used and discarded after the battery or e-liquid is depleted. They may also be a reusable device with a battery and cartridge called a cartomizer. The cartomizer cartridge can be separated from the battery so the battery can be charged and the empty cartomizer replaced when the e-juice runs out. The battery section may contain an electronic airflow sensor triggered by drawing breath through the device. Other models use a power button that must be held during operation. An LED in the power button or on the end of the device may also show when the device is vaporizing. Charging is commonly accomplished with a USB charger that attaches to the battery. Some manufacturers also have a cigarette pack-shaped portable charging case (PCC), which contains a larger battery capable of recharging the individual e-cigarette batteries. Reusable devices can come in a kit that contains a battery, a charger, and at least one cartridge. Varying nicotine concentrations are available and nicotine delivery to the user also varies based on different cartomizers, e-juice mixtures, and power supplied by the battery. These manufacturing differences affect the way e-cigarettes convert the liquid solution to an aerosol, and thus the levels of ingredients, that are delivered to the user and the surrounding air for any given liquid. First-generation e-cigarettes use lower voltages, around 3.7 V. Second-generation PV. Second generation devices tend to be used by people with more experience. They are larger overall and look less like tobacco cigarettes. They usually consist of two sections, basically a tank and a separate battery. Their batteries have higher capacity, and are not removable. Being rechargeable, they use a USB charger that attaches to the battery with a threaded connector. Some batteries have a "passthrough" feature so they can be used even while they are charging. Second-generation e-cigarettes commonly use a tank or a "clearomizer". Clearomizer tanks are meant to be refilled with e-juice, while cartomizers are not. Because they're refillable and the battery is rechargeable, their cost of operation is lower. Hovever, they can also use cartomizers, which are pre-filled only. Some cheaper battery sections use a microphone that detects the turbulence of the air passing through to activate the device when the user inhales. Other batteries like the eGo style can use an integrated circuit, as well as a button for manual activation. The LED shows battery status. The power button can also switch off the battery so it is not activated accidentally. Second generation e-cigarettes may have lower voltages, around 3.7 V. However, adjustable-voltage devices can be set between 3 V and 6 V. Third-generation PV. The third-generation includes mechanical mods and variable voltage devices. Battery sections are commonly called "mods," referencing their past when user modification was common. Mechanical mods do not contain integrated circuits. They are commonly cylindrical or box-shaped, and typical housing materials are wood, aluminium, stainless steel, or brass. A larger "box mod" can hold bigger and sometimes multiple batteries. Mechanical mods and variable devices use larger batteries than those found in previous generations. Common battery sizes used are 18350, 18490, 18500 and 18650. The battery is often removable, so it can be changed when depleted. The battery must be removed and charged externally. Variable devices permit setting wattage, voltage, or both. These often have a USB connector for recharging; some can be used while charging, called a "passthrough" feature. Mechanical mods do not contain integrated circuits. The power section may include additional options such as screen readout, support for a wide range of internal batteries, and compatibility with different types of atomizers. Third-generation devices can have rebuildable atomizers with different wicking materials. These rebuildables use handmade coils that can be installed in the atomizer to increase vapor production. Hardware in this generation is sometimes modified to increase power or flavor. The larger battery sections used also allow larger tanks to be attached that can hold more e-liquid. Recent devices can go up to 8 V, which can heat the e-liquid significantly more than earlier generations. A fourth-generation e-cigarette became available in the U.S. in 2014. Fourth-generation e-cigarettes can be made from stainless steel and pyrex glass, and contain very little plastics. Included in the fourth-generation are Sub ohm tanks and temperature control devices. An e-cigarette atomizer with the coil (heating element) in view. An atomizer comprises a small heating element that vaporizes e-liquid and a wicking material that draws liquid onto the coil. Along with a battery and e-liquid the atomizer is the main component of every personal vaporizer. A small length of resistance wire is coiled around the wicking material and connected to the integrated circuit, or in the case of mechanical devices, the atomizer is connected directly to the battery through either a 510, 808, or ego threaded connector. 510 being the most common. When activated, the resistance wire coil heats up and vaporizes the liquid, which is then inhaled by the user. The electrical resistance of the coil, the voltage output of the device, the airflow of the atomizer and the efficiency of the wick all affect the vapor coming from the atomizer. They also affect the vapor quantity or volume yielded. Atomizer coils made of kanthal usually have resistances that vary from 0.4Ω (ohms) to 2.8Ω. Coils of lower ohms have increased vapor production but could risk fire and dangerous battery failures if the user is not knowledgeable enough about electrical principles and how they relate to battery safety. Wicking materials vary from one atomizer to another. "Rebuildable" or "do it yourself" atomizers can use silica, cotton, rayon, porous ceramic, hemp, bamboo yarn, oxidized stainless steel mesh and even wire rope cables as wicking materials. A 45mm length, extra-long cartomizer. The cartomizer was invented in 2007, integrating the heating coil into the liquid chamber. A "cartomizer" (a portmanteau of cartridge and atomizer.) or "carto" consists of an atomizer surrounded by a liquid-soaked poly-foam that acts as an e-liquid holder. They can have up to 3 coils and each coil will increase vapor production. The cartomizer is usually discarded when the e-liquid starts to taste burnt, which usually happens when the e-cigarette is activated with a dry coil or when the cartomizer gets consistently flooded (gurgling) because of sedimentation of the wick. Most cartomizers are refillable even if not advertised as such. Cartomizers can be used on their own or in conjunction with a tank that allows more e-liquid capacity. The portmanteau word "cartotank" has been coined for this. When used in a tank, the cartomizer is inserted in a plastic, glass or metal tube and holes or slots have to be punched on the sides of the cartomizer so liquid can reach the coil. eGo style e-cigarette with a top-coil clearomizer. Silica fibers are hanging down freely inside of the tank, drawing e-liquid by capillary action to the coil that is located directly under the mouthpiece. The clearomizer was invented in 2009 that originated from the cartomizer design. It contained the wicking material, an e-liquid chamber, and an atomizer coil within a single clear component. This allows the user to monitor the liquid level in the device. Clearomizers or "clearos", are like cartotanks, in that an atomizer is inserted into the tank. There are different wicking systems used inside clearomizers. Some rely on gravity to bring the e-liquid to the wick and coil assembly (bottom coil clearomizers for example) and others rely on capillary action or to some degree the user agitating the e-liquid while handling the clearomizer (top coil clearomizers). The coil and wicks are typically inside a prefabricated assembly or "head" that is replaceable by the user. Clearomizers are made with adjustable air flow control. Tanks can be plastic or borosilicate glass. Some flavors of e-juice have been known to damage plastic clearomizer tanks. Box mod e-cigarette fitted with a rebuildable dripping atomizer (RDA). A view of the RDA deck showing the wicks and coils, juice is dripped into a hopper where the wicks rest as well as atop the coil assembly. A rebuildable atomizer or an RBA is an atomizer that allows the user to assemble or "build" the wick and coil themselves instead of replacing them with off-the-shelf atomizer "heads". They are generally considered advanced devices. They also allow the user to build atomizers at any desired electrical resistance. These atomizers are divided into two main categories; rebuildable tank atomizers (RTAs) and rebuildable dripping atomizers (RDAs). Rebuildable tank atomizers (RTAs) have a tank to hold liquid that is absorbed by the wick. They can hold up to 4ml of e-liquid. The tank can be either plastic, glass, or metal. One form of tank atomizers was the Genesis style atomizers. They can use ceramic wicks, stainless steel mesh or rope for wicking material. The steel wick must be oxidized to prevent arcing of the coil. Another type is the Sub ohm tank. These tanks have rebuildabe or RBA kits. They can also use coilheads of 0.2ohm 0.4hom and 0.5ohm. These coilheads can have stainless steel coils. Rebuildable dripping atomizers (RDAs) are atomizers where the e-juice is dripped directly onto the coil and wick. The common nicotine strength of e-liquids used in RDA's is 3 mg and 6 mg. Liquids used in RDA's tend to have more vegetable glycerin. They typically consist only of an atomizer "building deck", commonly with three posts with holes drilled in them, which can accept one or more coils. The user needs to manually keep the atomizer wet by dripping liquid on the bare wick and coil assembly, hence their name. Kanthal wire is commonly used in both RDA's and RTA's. They can also use nickel wire or titanium wire for temperature control. Variable devices are variable wattage, variable voltage or both. Variable power and/or variable voltage have a electronic chip allowing the user to adjust the power applied to the heating element. The amount of power applied to the coil affects the heat produced, thus changing the vapor output. Greater heat from the coil increases vapor production. Variable power devices monitor the coil's resistance and automatically adjust the voltage to apply the user-specified level of power to the coil. Recent devices can go up to 8 V. They are often rectangular but can also be cylindrical. They usually have a screen to show information such as voltage, power, and resistance of the coil. To adjust the settings, the user presses buttons or rotates a dial to turn the power up or down. Some of these devices include additional settings through their menu system such as: atomizer resistance meter, remaining battery voltage, puff counter, and power-off or lock. The power source is the biggest component of an e-cigarette, which is frequently a rechargeable lithium-ion battery. Smaller devices contain smaller batteries and are easier to carry but typically require more repeated recharging. Some e-cigarettes use a long lasting rechargeable battery, a non-rechargeable battery or a replaceable battery that is either rechargeable or non-rechargeable for power. Some companies offer portable chargeable cases to recharge e-cigarettes. Nickel-cadmium (NiCad), nickel metal-hydride (NiMh), lithium ion (Li-ion), alkaline and lithium polymer (Li-poly), and lithium manganese (LiMn) batteries have been used for the e-cigarettes power source. PV with variable and regulated power offering battery protection. Temperature control devices allow the user to set the temperature. There is a predictable change to the resistance of a coil when it is heated. The resistance changes are different for different types of wires, and must have a high temperature coefficient of resistance. Temperature control is done by detecting that resistance change to estimate the temperature and adjusting the voltage to the coil to match that estimate. Nickel, titanium, NiFe alloys, and certain grades of stainless steel are common materials used for wire in temperature control. The most common wire used, kanthal, cannot be used because it has a stable resistance regardless of the coil temperature. Nickel was the first wire used because of it has the highest coefficient of the common metals. Mechanical PV with a rebuildable atomizer. The temperature can be adjusted in Celsius or Fahrenheit. The DNA40 and SX350J are common control boards used in temperature control devices. Temperature control can stop dry wicks from burning, or e-liquid overheating. Mechanical PVs or mechanical "mods", often called "mechs", are devices without integrated circuits, electronic battery protection, or voltage regulation. They are activated by a switch. They rely on the natural voltage output of the battery and the metal that the mod is made of often is used as part of the circuit itself. The term "mod" was originally used instead of "modification". Users would modify existing hardware to get better performance, and as an alternative to the e-cigarettes that looked like traditional cigarettes. Users would also modify other unrelated items like flashlights as battery compartments to power atomizers. The word mod is often used to describe most personal vaporizers. Mechanical PVs have no power regulation and are unprotected. Because of this ensuring that the battery does not over-discharge and that the resistance of the atomizer requires amperage within the safety limits of the battery is the responsibility of the user.