Rotovap questions

GNYC said:

lol with such a large amount we've always just hooked a hose from the fractional to the injection port for the roto and put an extra long injection tube on first inside the ball. then turned on the vac on the fractional and pulled as much as we could via the hose and then rehooked everything back up and went about our jobs. we wouldn't get it all out of the roto and wouldn't worry about it unless we switched strains or parameters of something. then we would do exactly as you listed above.

Click to expand...

I have a question about ethanol distillation, but not using a roto. Say that I have a 5 liters to distill using a 2l mantle, which I would do in 3-4 runs. When I start the process and pull vacuum, temps drop in the flask to the high 50s F and as the ethanol evaporates over an hour temps rise to the 90s. I am trying to keep terpenes, so high temps are bad. I found that once I get to ~90% evaporation temps can really shoot up fast (over 100F) if my mantle is too hot, but if I don't push temps than purge is too runny to start.

So my question is this: Is it advantageous to just leave the extract in my boiling flask (at 80-85% etoh evaporation) and then add another liter or so of solution to flask each time temps reach 90s until gone? Logic would be that I only have to push temps higher once and a larger volume of extract mass could reduce the explosive out gassing that splatters the walls of flask towards end.

I appreciate any insight.

WFF

Before rotovape, we distilled off large quantities to the syrupy "bumping" stage and finished off in a vacuum oven using a shallow dish with a sheet of glass over the top to catch the bumps.

If you combine them all for the final finish, you should limit the heat cycling.

Gray Wolf said:

Before rotovape, we distilled off large quantities to the syrupy "bumping" stage and finished off in a vacuum oven using a shallow dish with a sheet of glass over the top to catch the bumps.

If you combine them all for the final finish, you should limit the heat cycling.

Click to expand...

Thanks. Is "combine them all for the final finish" the same as never pouring out extract until very end of distillation? I really don't want to disassemble distillation rig each time to pour out until finished and just use the second neck with 24/40 funnel to add additional etoh solution until gone.

WaterFarmFan said:

Thanks. Is "combine them all for the final finish" the same as never pouring out extract until very end of distillation? I really don't want to disassemble distillation rig each time to pour out until finished and just use the second neck with 24/40 funnel to add additional etoh solution until gone.

Click to expand...

I was suggesting pouring off the syrup each time but combining them wouldn't be a disaster.

Some decarboxylation occurs with boiling, but shouldn't be a lot if you're down to -28" Hg, which ostensibly is around 19C/66F.

I've only ever used a rotovap so I would definitely take GW's advice his science is solid behind the explanation.

Gray Wolf said:

Before rotovape, we distilled off large quantities to the syrupy "bumping" stage and finished off in a vacuum oven using a shallow dish with a sheet of glass over the top to catch the bumps.

If you combine them all for the final finish, you should limit the heat cycling.

Click to expand...

by syrupy bumping stage you mean when it starts to congeal into the solid mass you'd add to your mantle? Everyone uses different terminology when discussing stages/states of the fluid in the process lol. I'm just trying to make sure I understand that you are purging your ethanol via vac oven? If so the glass plate over top is to reclaim ethanol, or is it to help retain heat?

GNYC said:

I've only ever used a rotovap so I would definitely take GW's advice his science is solid behind the explanation.



by syrupy bumping stage you mean when it starts to congeal into the solid mass you'd add to your mantle? Everyone uses different terminology when discussing stages/states of the fluid in the process lol. I'm just trying to make sure I understand that you are purging your ethanol via vac oven? If so the glass plate over top is to reclaim ethanol, or is it to help retain heat?

Click to expand...

The glass plate is to catch the spatter from the explosive burst (bumping). It is easy to remove from the sheet of glass with a razor blade, but not so easy from all over the inside of the oven.

Gray Wolf said:

Before rotovape, we distilled off large quantities to the syrupy "bumping" stage and finished off in a vacuum oven using a shallow dish with a sheet of glass over the top to catch the bumps.

If you combine them all for the final finish, you should limit the heat cycling.

Click to expand...

This is the first time I've seen someone mention covering the dish in the vacuum oven, would using parchment paper work just as well or is it not heavy enough? I have a few Pyrex baking dish that I've been itching to give a shot, we control the boiling enough to prevent it from boiling over, but small splatters are inevitable and a small plate of glass or parchment would save a ton of cleaning.

GNYC said:

by syrupy bumping stage you mean when it starts to congeal into the solid mass you'd add to your mantle? Everyone uses different terminology when discussing stages/states of the fluid in the process lol. I'm just trying to make sure I understand that you are purging your ethanol via vac oven? If so the glass plate over top is to reclaim ethanol, or is it to help retain heat?

Click to expand...

I understand syrupy bumping stage to be somewhere around 90% removal of etoh, and it's where the extract solution goes from a thin liquid to runny syrup, and it can happen quite fast. You know you are there when extract starts occasional explosive splattering that coats the boiling flask in a thin film. Temps can shoot up 20F inside the flask within a few minutes. I try to time the very beginning of this stage (in order to not ramp temps to preserve terpenes) and remove the flask from mantle to pour out extract for purge in a vacuum oven.

So i've only ever made oil with my crude using a Closed Loop BHO system winterization filtration and then solvent extraction using the 20 L rotovap (pic below). That being said, i've always left it slightly viscous in order to get it to transfer smoothly to the fractional distillation mantle. I would just purge the last remaining small percentage of ethanol there w/ the first fraction of terps (since they are pretty much ruined from the bho/fractional distillation process). I guess I could do what GW suggested and put the syrup in a pyrex in a vac oven and put a glass plate on top and purge completely, but I don't know what the benefits would be comparably in methods to doing this. I don't think i've every brought it down in the roto to the point where it bumps only time I've ever brought it to such a stage would be in the fractional mantle. I am currently looking into CO2 extraction systems so i can do Fractional Separation rather than straight to fractional distillation so i can as you would like to preserve the terps. then go back and refine after combining the different fractions back together w/o terps and put them through fractional distillation and upon completion of that process reintroduce the natural terpene profile back to the end product. Unless I have the whole process confused of how it works? I've only been doing this for a year and ever since finding this treasure trove of a forum I feel so far behind compared to people like GW, Sky, Pangea, and others so I'm always up to hear how anyone else is attaining their desired end result.

whatthe215 said:

Both. My recommendation for flasks with a large enough opening (China 20L and 50L flasks) is this:

- Buy arm gloves, the kind for inseminating cows and some rubber bands to hold it at shoulder. Have silicone spatulas.

a) Finish rotovaping @ ~60c, kill vac, stop rotation, insert stopping key (so it doesn't rotate when you unscrew,) then let sit for 10-15min so oil can collect from walls and get to temperature 60c.

b) Remove evap flask and pour out as much oil as you can. Let sit upside down for 5-10min dripping into collection container. Use heat gun carefully if desired.

c) Turn evap flask so that you can reach in with arm glove and spatula and scrape out as much as you can. After the first time you'll probably dial in the method. I scrape the top first so I can see inside. Scrape upwards and then pull the oil covered spatula out and deposit into collection container.

** You'll dial in time to wait before starting spatula scraping depending on oil consistency/type. Too early = too hot for your arm and oil will fall right off spatula, too late = very difficult to scrape, more left behind. There's a perfect 5 or 10 min window. **

d) Use minimum amount of ethanol/solvent required to dissolve left over oil in flask. Save it for rainy day, put it in your ultrasonic solvent bath, whatever. Rotovap once you've got enough and need the solvent back. Squirt bottles help. Using arm gloved hand to swish solvent around and rub sides helps tremendously.

Done properly and with fresh arm gloves, I can't imagine a cGMP inspector or whatever having much of an issue with this method, although it may seem a bit ghetto.


Alternatively, throw away the rotovap and get an industrial solvent recycling machine.

Click to expand...

SkyHighLer said:

"Alternatively, throw away the rotovap and get an industrial solvent recycling machine."


There is no reason to use a rotovac to rip solvent when the oil is going to be fractionated.

Rotovacs are extremely dangerous, and extremely expensive, and are invaluable in the lab, where they belong, these are not generally meant for production situations when viable alternatives exist.

Rather than step all the way up to industrial solvent recovery systems, there is a line of common commercial solvent recovery systems that should do nicely, they are referred to as solvent recyclers.

The smallest, 3-5 gallon units are used for such things as automobile paint shop in-house solvent recovery, machine shops, etc.

Much larger sizes, and various options, including vacuum/feed/removal are available.

The smaller units use nylon or Teflon bags, remove the bag, cut a corner, and let it drain, squeegee all but the very the last out.

These units have advanced controls to allow the use of solvents with various boiling points. (The new controllers with both power and temperature control would be better yet, recently I've proven to myself that floating the temperature at the boiling point, and adjusting the boiling level by regulating the power available to the heater is far smoother than trying to control the boiling with PID temperature control alone. This goes for your Buchi and Heidolph rotovapes too, lol.)


BECCA SS17.5 (17.5 Gal) Solvent Distillation Recycler - Features

https://www.youtube.com/watch?v=m8jgVCHO-Gw


BECCA HC (6 Gal) & SC (3 Gal) Solvent Distillation Recycler - Features

https://www.youtube.com/watch?v=_NDX8GghGrk


Sidewinder Model M2 Presentation

https://youtu.be/q-bM74dCZ4k?t=33s

Click to expand...

I've been try to stoke up interest in commercial/industrial solvent recovery machines for a couple of years here at ICMAG Concentrate Forums...

https://labsociety.com/lab-equipment/solvent-recovery/


Automated Solvent Recovery System (ASRS)
from: $57,190.00

– Lab Society

Solvent Recycle

Recover more solvents than you ever thought possible.

Our top-of-the-line Automated Solvent Recovery System (ASRS) was designed to meet the needs of even the most demanding of industrial laboratories. Instead of letting valuable solvents go to waste, you can now easily recover them on a larger scale than ever before.

High volume lab? Not to worry.

Early real-world tests show that these units perform well beyond specifications, letting you recover more of your solvent per hour than by any other method on the market.

Finally, a plug-and-play solution for top-of-the-line labs.

Thanks to a variety of sensors and automations at the heart of these machines, all of our (ASRS) units are able to run safely with minimal operator intervention. For busy lab owners, this product is a game changer. In most cases, it’s a simple matter of plug and play.

Features:

set it and forget it – Just put the used solvent in, and watch the clean solvent come out.
multiple, large-scale sizes – (32, 50, 75, 110 Gallon options available)
process insane amounts of solvent per hour – (5.5, 9.1, 16.6, 18.2 gallons per hour, respectively)
vacuum-assisted – Allows for a reduced atmosphere, which lowers boiling points and increases evaporation speed!
remotely accessible via ethernet or cellular data
electric heating (with thermal oil)
collection container sensors prevent overflow and spills
includes free lifetime service and support (including remote access)
480 volts – make sure you have the proper power available
automatic hydraulic tilt lift available upgrade
Shop Solvent Extraction Products Online

Vacuum assisted.

These powerful machines use a vacuum in the boiling chamber to lower the temperature needed to boil high-boiling-point solvents. Each premium unit uses a Liquid Ring Vacuum System for maximum efficiency.

Remotely accessible via ethernet or cellular data.

The system PLC is accessible remotely through an Ethernet or cellular data connection. Settings can be viewed and changed as if the touch screen was being used.

Electric heating (with thermal oil).

Uses a thermal oil jacket electric heater to quickly and evenly heat the boiling vessel.

Collection container sensors prevent overflow and spills.

The last thing you want is a massive solvent leak in your laboratory, or worse, volatile chemicals and vapors everywhere. That’s why we’ve integrated intelligent sensors to prevent spills and to stop these machines from overflowing.

Not only that, our automated premium solvent recovery units are:

Recycling Alcohol, Ethanol

Safe – Class 1, Div 1, Group D, explosion-proof, METLAB Certified
Strong – High quality 304 stainless steel construction
Simple – Automated operations, tilted base for easy residual product removal and access
Smart – Highly automated, with touch-screen PLC and remote cellular access
Note: The ASRS requires the use of a 480V standalone chiller.



Compare to the solvent recyclers that can be found at the Sidewinder and Becca sites,

https://solvent-recycler.com

https://www.beccainc.com/solvent-distillation-recycling-equipment/


I mentioned in the quote there are better controllers with both power and temperature controls now available that would provide smoother distillation. Shouldn't take an electrical genius to figure out how to swap out the controller, here's a post explaining the new controllers,

https://www.icmag.com/ic/showpost.php?p=8338634&postcount=22

The Auber controller referred to (either the DSPR220, or DSPR440 with relay output) drives a solid state relay, or two, or three, it can drive up to 5 or 6. The solid state relays are available in 3-Phase configuration, here's an 80A per Phase device from Auberins,

https://www.auberins.com/index.php?main_page=product_info&cPath=2_30&products_id=105

^ I started reading through the instruction manuals and other documentation, the Becca 17.5 gallon unit has a controller with both power and temperature control!!

https://www.beccainc.com/wp-content...all-Instruction-Maintenance-Manual-9-2015.pdf

Solvent SaverTM Recycler & Vacuum Assist Systems
Installation, Instruction & Maintenance Manual
Approved to UL std 2208 & Class I Div 1
BECCA Inc.
2010 Cobb International Parkway Kennesaw, GA 30153
Phone: 1-800-655-5649 Fax: 1-800-655-5649 Beccainc.com
Model SS-17.5 17.5 Gallon Recycler


"TIME & TEMPERATURE SETTINGS – DESCRIPTION

Time and temperature are needed to obtain optimal results.

A) Set the temperature at least 50 oF higher than boiling point.

B) Set time accordingly to the product and the volume.
 BECCA Solvent Saver 17.5 will take approximately 3.5 – 5 hours (for most solvents) per batch.
If at the end of a cycle, there is still liquid, increase the distillation time by 25% for the next batch. If set for 4 hours, then increase to 5 hours. Never distill a product having an auto ignition point below 572oF (300oC).

C) Power adjustment
 The power is set at the factory at 100%. At the beginning of the distillation, the liquid must be cold when going out of the condenser. If the liquid is hot, the power of the element must be adjusted downwards. Lower the power by 10 degrees at the time and check to see if liquid is cold. When it becomes cold, the power is properly adjusted."


"The condensed solvent coming out of the condenser should be cool. Should the unit be located in a well-ventilated area and the liquid coming out warm, this means that the distillation is done too fast. You need to lower the intensity of the element by reducing the power level of the controller, which has been set at 100% of its power. Should you need to reduce it, do it 10% at a time until the liquid comes out cool."



Becca's 55 gallon unit also has a controller with both power and temperature control,

https://www.beccainc.com/wp-content...ion-Instruction-Maintenance-Manual-9-2016.pdf

"The condensed solvent coming out of the condenser should be cool. Should the unit be located in a well-ventilated area and the liquid coming out warm, this means that the distillation is done too fast. You need to lower the intensity of the element by reducing the power level of the controller, which has been set at 100% of its power. Should you need to reduce it, do it 10% at a time until the liquid comes out cool."

"TO CHANGE POWER LEVEL
Enter the set-up menu by pressing the  Up-arrow and  Down-arrow keys simultaneously
for 3 seconds. The lower display shows the Lock parameter and the upper display
shows its current level. All keys are inactive until you release both keys. You can reach the Lock parameter from anywhere.
Use the  Scrolling key to move through the menus until you see PL in Lower display and
the  Up-arrow and  Down-arrow keys to select data (Factory set at 100%. Lower by 10 % and try again. If set too low, recycler might not bring solvent to boiling point)."


The links I provided all work, just use the trick in my Signature to open them.

Hi, I have a Heidolph rotavapor because I wanted to make cannabis essential oil. By the way, I also bought a vacum and a machine that gets the water cold.
I've got some drops of cannabis essential oil, but I spent a lot of time and I think it wasn´t worth it.
I do BHO, but I do not know how to purge it with the rotavapor.

Please, could anyone tell me how to purge my bho with the rotavapor?

Thanks very much

mccleud said:

Hi, I have a Heidolph rotavapor because I wanted to make cannabis essential oil. By the way, I also bought a vacum and a machine that gets the water cold.
I've got some drops of cannabis essential oil, but I spent a lot of time and I think it wasn´t worth it.
I do BHO, but I do not know how to purge it with the rotavapor.

Please, could anyone tell me how to purge my bho with the rotavapor?

Thanks very much

Click to expand...

A rotovape is typically not used to purge BHO concentrate, but is used to remove solvents like alcohol, pentane, hexane, heptane, etc.


Here is an article where we tested the Heidolph removing ethanol after winterizing BHO.


https://web.archive.org/web/2016012...heidolph-instruments-hei-vap-precision-ml-g3/

Thanks Gray_Wolf,

Your url address does not work.

So, if I purge my bho concentrate, and then I add alcohol to my bho and then I remove the alcohol with my rotavapor... then my bho would not have the unhealthy things coming from the butane gas.

Is this correct?

Thanks very much for your help

mccleud said:

Thanks Gray_Wolf,

Your url address does not work.

So, if I purge my bho concentrate, and then I add alcohol to my bho and then I remove the alcohol with my rotavapor... then my bho would not have the unhealthy things coming from the butane gas.

Is this correct?

Thanks very much for your help

Click to expand...

Assuming you predistilled the LPG to remove any mystery oil before extracting, the alcohol wash will remove the rest of the butane.

As another layer of assurance, both butane, propane, and ethanol are all listed as GRAS by FDA.

Thanks for the answer Gray Wolf,

Could you tell me what LPG mean? I found out GRAS by myself.

I have found your article explaining how you can use the rotavapor in order to remove the alcohol. I think this is easy.
https://skunkpharmresearch.com/evaluation-of-heidolph-instruments-hei-vap-precision-ml-g3/

1. Add 500 ml of BHO/ethanol mixture to the evaporating flask. Note that greater volumes may be appropriate in situations where a larger flask is used but care should be taken as to avoid filling the flask over half full.

2. Lock the flask into place on the rotary valve and lower the unit into the warming bath.

3. Set the temperature of the bath to 25ºC.

4. Set the rotation of the flask at 160 rpm. Note that faster speeds may be achievable in a larger flask but operators noticed that higher rotational speeds in the 1 L flask resulted in excessive bumping.

5. Set the initial vacuum level to 80 mbar to begin the process. Increase the vacuum over the course of the distillation as follows.

a. 0-1 min: Pull down for atmospheric pressure to 80 mbar.

b. 1-5 min: Hold at 80 mbar.

c. 5-10 min: Reduce pressure to 60 mbar, hold. At 10 min, about 50 ml of ethanol should have been reclaimed.

d. 10-15 min: Reduce pressure 40 mbar, hold. At 15 min, about 100 ml of ethanol should have been reclaimed.

e. 15-45 min. Reduce pressure to 20 mbar, hold. Vacuum does not exceed 20 mbar but will remain on constantly at this point. At 45 min, about 450 ml of ethanol should have been reclaimed. Note that it is important to leave some ethanol behind so as to be able to easily remove the remaining material from the evaporation flask.

f. The material is collected, spread on PTFE sheets, and placed in the vacuum oven to complete final purge.


Could you tell me what other things can I do with the rotavapor? Things related to cannabis. Is there a way to separate THC from CBD?

Thanks very much!!

mccleud said:

Thanks for the answer Gray Wolf,

Could you tell me what LPG mean? I found out GRAS by myself.

I have found your article explaining how you can use the rotavapor in order to remove the alcohol. I think this is easy.
https://skunkpharmresearch.com/evaluation-of-heidolph-instruments-hei-vap-precision-ml-g3/

1. Add 500 ml of BHO/ethanol mixture to the evaporating flask. Note that greater volumes may be appropriate in situations where a larger flask is used but care should be taken as to avoid filling the flask over half full.

2. Lock the flask into place on the rotary valve and lower the unit into the warming bath.

3. Set the temperature of the bath to 25ºC.

4. Set the rotation of the flask at 160 rpm. Note that faster speeds may be achievable in a larger flask but operators noticed that higher rotational speeds in the 1 L flask resulted in excessive bumping.

5. Set the initial vacuum level to 80 mbar to begin the process. Increase the vacuum over the course of the distillation as follows.

a. 0-1 min: Pull down for atmospheric pressure to 80 mbar.

b. 1-5 min: Hold at 80 mbar.

c. 5-10 min: Reduce pressure to 60 mbar, hold. At 10 min, about 50 ml of ethanol should have been reclaimed.

d. 10-15 min: Reduce pressure 40 mbar, hold. At 15 min, about 100 ml of ethanol should have been reclaimed.

e. 15-45 min. Reduce pressure to 20 mbar, hold. Vacuum does not exceed 20 mbar but will remain on constantly at this point. At 45 min, about 450 ml of ethanol should have been reclaimed. Note that it is important to leave some ethanol behind so as to be able to easily remove the remaining material from the evaporation flask.

f. The material is collected, spread on PTFE sheets, and placed in the vacuum oven to complete final purge.


Could you tell me what other things can I do with the rotavapor? Things related to cannabis. Is there a way to separate THC from CBD?

Thanks very much!!

Click to expand...

Liquefied Petroleum Gas. I used that instead of the word butane, because many of us use a mix.

No way I'm aware of to separate THC and CBD using a rotovape.

They are designed to maximize thin film surface area under vacuum, so as to remove volatile vapors at lower temperatures than at atmospheric pressure.

Thanks Gray Wolf,

I have never heard about LPG method. I will look for it.
I am very satisfied for your explanations because now I can make a healthy BHO concentrate.
The GRAS thing of the FDA is not good enough for me.

Regards!

mccleud said:

Thanks Gray Wolf,

I have never heard about LPG method. I will look for it.
I am very satisfied for your explanations because now I can make a healthy BHO concentrate.
The GRAS thing of the FDA is not good enough for me.

Regards!

Click to expand...

LPG is typically referred to as BHO, although it may include mixed gasses, not just butane.

If you remove the mystery oil first by pre-distilling your LPG, and remove the residual solvent using heat and vacuum, the resulting concentrate is as salubrious as ethanol, which is also GRAS.

FDA requires residual butane/propane to be below 5000 ppm, but you can taste it well below that level and production standards are typically set at 10% or less of that level.

The greatest danger with LPG is its flammability and explosive properties, so close attention to detail is required to avoid conflagration.

See https://www.icmag.com/ic/showthread.php?t=212613

mccleud said:

Thanks Gray Wolf,

I have never heard about LPG method. I will look for it.
I am very satisfied for your explanations because now I can make a healthy BHO concentrate.
The GRAS thing of the FDA is not good enough for me.

Regards!

Click to expand...

This probably won't convince you of anything, but it is the conclusion of the mainstream scientific community.


Encyclopedia of Toxicology, Volume 1, page 572

Butane

Background
Butane is a widely used compound, most commonly as a fuel in lighters, torches, and stoves. Although it is an asphyxiant when inhaled in large amounts, it has been used in smaller amounts by those looking for substances that can produce altered mental states. Such abuse of butane has resulted in a number of deaths from what is known as Sudden Sniffing Death Syndrome.

Exposure Routes and Pathways
Since butane is a gas, the major routes of exposure are inhalation and contact with skin and eyes. It is a widely used substance of abuse by inhalation.

Mechanism of Toxicity
Gaseous butane acts as a simple asphyxiant, which means that it causes toxicity by displacing oxygen and preventing it from reaching important tissues and organs. In its liquid state, it causes frostbite due to rapid cooling on evaporation.

Acute and Short-Term Toxicity
Animal
An LC50 of 658 g m��3, for a 4-h inhalation exposure, has been established in rats.

Human
Because of its asphyxiant properties, high doses of inhaled butane can affect the central nervous system and lead to a variety of symptoms. These include euphoria, excitation, vomiting, confusion, hallucinations, drowsiness, and coma. Skin contact with liquid butane can cause frostbite.

Clinical Management
The affected person should be removed from exposure and provided fresh air. Symptomatic and supportive treatment should be administered. This may include support of both cardiovascular and respiratory systems.

Exposure Standards and Guidelines
The American Conference of Governmental Industrial Hygienists time-weighted average (TWA) for butane is 800ppm (1900mgm3) and the TWA for liquefied petroleum gas is 1000 ppm (1800 mg m3).



Encyclopedia of Toxicology, Volume 3, pages 1086-1088

Propane

Toxicokinetics
Inhaled n-propane is rapidly distributed from the blood to different organs and tissues, particularly those with high fat content. The metabolic elimination rate of propane has been shown to be dependent on the atmospheric concentration. In mice, propane was converted to isopropanol and acetone following inhalation. In the presence of microsomes prepared from liver homogenate of mice, the test substance was also converted in vitro to isopropanol. The oxidation of isopropanol to acetone occurred in the presence of alcohol dehydrogenase. The metabolites were detected in blood, liver, kidney, and brain of the exposed mice.

Mechanism of Toxicity
Some sources classify propane as a simple anesthetic, although it can principally be classified as a simple asphyxiant. Concentrations that are high enough to displace oxygen would be expected to cause lightheadedness, loss of consciousness, and possibly death from asphyxiation.

Animal
Propane has been shown to have adverse effects on the cardiovascular system in the primate, dog, cat, and mouse. Guinea pigs exposed to 2.2–5.5% of the gas showed sniffing and chewing movements. In dogs, 1% caused hemodynamic changes, whereas 3.3% produced decreases in aortic pressure, stroke volume, and cardiac output and an increase in pulmonary resistance. Ten percent propane in the mouse and 15% in the dog did not produce arrhythmia but did produce weak cardiac sensitization.

Human
Propane is not considered to be inherently toxic to humans. Air concentrations up to 10 000 ppm (10%) for a few minutes will only produce slight dizziness in humans. At high concentrations, it may have a narcotic effect; but at concentrations below 100 ppm, propane causes no physiological effects in humans. However, it will cause chemical suffocation at concentrations that are high enough to displace oxygen.

Immunotoxicity
A comprehensive search on the adverse immunotoxic effects of propane on the immune system could not find any studies in the public domain.

Reproductive Toxicity
A comprehensive search on the adverse reproductive effects of propane on the immune system could not find any studies in the public domain. Pregnant women should, however, avoid inhalation of any type of petroleum solvent vapors.

Carcinogenicity
Propane is not listed as a carcinogen by the National Toxicology Program, the Occupational Safety and Health Administration, or the International Agency for Research on Cancer.

Clinical Management
Persons who are exposed to high concentrations of propane in air should vacate or be removed from the source and seek fresh air. In areas of expected increased concentration, extreme care must be taken to use explosion-proof apparatus and keep the areas free from ignition sources, such as sparks from static electricity.

Exposure Standards and Guidelines
The US Food and Drug Administration classifies propane as generally recognized as safe. Propane has an Occupational Safety and Health Administration 8-h time-weighted average (TWA) of 1000 ppm (1800 mg m��3). The American Conference of Governmental Industrial Hygienists 8-h TWA is 1000 ppm (based on aliphatic hydrocarbon gases, C1–C4). NIOSH’s recommended exposure limit is also a 10-h TWA of 1000 ppm (1800 mg m��3). The level of propane that is ‘Immediately Dangerous to Life and Health’ is 2100 ppm (based on 10% of the lower explosive limit for safety considerations even though the relevant toxicological data indicated that irreversible health effects or impairment of escape existed only at higher concentrations).