Jennifer, I'm not an expert on the health effects of closed cell foam. A lot of people live in houses with closed cell foam and have no health problems from it, at least not short-term, acute problems. I do know of one person who had it removed from her crawl space because she was convinced it caused her dog to get sick, but I know only what she told me.   Spray Coating
Synavax™ thermal insulation coatings help organizations improve energy efficiency. They are nano-engineered patented cutting-edge thermal paint coatings that provide next generation performance beyond older, non-patented ceramic insulation products.  Additionally, our products are eco-friendly and provide mold-resistant and anti-condensation properties without harmful biocides and other harsh chemicals, which is a significant plus for sustainably-minded companies. Spray Coating Services
Steve: If your spray foam installer leaves the vents open, he will be committing the 2nd of the 4 problems I described above. You will most likely have comfort and efficiency problems. You may well have condensation problems. You will be spending a lot of money on a product that likely won't perform as it should. Don't let him leave the vents open. If the installer you've chosen doesn't understand this, you may want to choose someone else. 
Fiberglass is the giant in the insulation industry, and the R rating to which it conforms is ingrained in the minds of contractors, builders, and code inspectors. Insulating ceramic coatings offer an alternative to traditional batt insulation. “Fiberglass insulation is tested and rated at 73 degrees Fahrenheit, which is the ideal temperature for fiberglass,” says Pritchett. Under harsher conditions, Pritchett suggests that fiberglass doesn’t perform as well as its ratings predict.
While intumescent coating can be used instead of an ignition barrier or thermal barrier in some cases, the coating itself is not technically either. It does prevent or slow fires, so it has been approved to be used in conjunction with spray foaminsulation as an alternate assembly. The fact that it qualifies as an alternate assembly means that it can be used instead of a thermal barrier or ignition barrier. Coating Services
This technique is mostly used to produce coatings on structural materials. Such coatings provide protection against high temperatures (for example thermal barrier coatings for exhaust heat management), corrosion, erosion, wear; they can also change the appearance, electrical or tribological properties of the surface, replace worn material, etc. When sprayed on substrates of various shapes and removed, free-standing parts in the form of plates, tubes, shells, etc. can be produced. It can also be used for powder processing (spheroidization, homogenization, modification of chemistry, etc.). In this case, the substrate for deposition is absent and the particles solidify during flight or in a controlled environment (e.g., water). This technique with variation may also be used to create porous structures, suitable for bone ingrowth, as a coating for medical implants. A polymer dispersion aerosol can be injected into the plasma discharge in order to create a grafting of this polymer on to a substrate surface.[3] This application is mainly used to modify the surface chemistry of polymers. Spray Coating
Open cell spray foams are less common and have a lower resistance to heat flow than closed cell spray does. Open cell spray foaminsulation expands when it is applied, which allows it to be installed in hard to reach areas, such as small wall and ceiling cavities. Open-cell spray foam is typically cheaper than closed cell foam is, but it is more permeable and vulnerable to fire hazards.
In the case you have above the installer wasn't reading his foam. They must be trained to do that as they spray. Temps and conditions are constantly changing thru out the day. Either he wasn't properly trained or if he was,he wasn't doing his job! This is a serious problem with people jumping in to the foam business. A lot of homeowners and builders are looking the best price and end up with someone who doesn't know what they are doing. Hope this info helps. Foam insulation is a great product. It just has to be done right by someone who knows what they are doing.
Combustion spraying guns use oxygen and fuel gases. The fuel gases are potentially explosive. In particular, acetylene may only be used under approved conditions. Oxygen, while not explosive, will sustain combustion, and many materials will spontaneously ignite, if excessive oxygen levels are present. Care must be taken to avoid leakage, and to isolate oxygen and fuel gas supplies, when not in use.[6] Spray Coating
There have been a few mentions of intumescent coatingsabove, and it would be helpful to elaborate on them. Intumescent coating is a type of paint that will bubble when it is exposed to heat or flames. The bubbles act as a barrier that is relatively flame resistant. The bubbled coating delays the ignition of the spray foaminsulation. Because of this, intumescent coatings have become more common in building and construction. Insulation Spray Coating
There is a significant price difference when it comes to using foam insulation to insulate a new versus older home. Spraying insulation inside a newly constructed home is easier because the installation company can ensure the insulation will work effectively and design it for optimum defense against sound, heat transfer and utility costs. Installing spray foam in older homes that contain existing insulation can cost additional time and money -- it is not usually recommended as compared to weatherization or an energy aduit.

Charles spoke of a "huge problem" of convection within cavities not filled with foam. This is a false assertion. The trillions of trapped air cells in foam insulation prevent heat transfer at a rate that would cause those problems. Also the wood framing members are relatively good insulators themselves unless the wood is particularly dense. Convection currents against foam insulation are not the problem he asserts. He also said" the homeowner is literally pissing money away if he pays for this spray foam job - or any job like it - for he will only be gaining a marginal amount of insulation effectiveness." This is a ludicrous statement. The structure pictured above will have a very effective performance despite his assertions. My only concern is humidity. Closed cell foam does not permit moisture migration and trapped moisture could be a problem, especially if the AC is not running due to moderate to cold temperatures.

During the 1980s, a class of thermal spray processes called high velocity oxy-fuel spraying was developed. A mixture of gaseous or liquid fuel and oxygen is fed into a combustion chamber, where they are ignited and combusted continuously. The resultant hot gas at a pressure close to 1 MPa emanates through a converging–diverging nozzle and travels through a straight section. The fuels can be gases (hydrogen, methane, propane, propylene, acetylene, natural gas, etc.) or liquids (kerosene, etc.). The jet velocity at the exit of the barrel (>1000 m/s) exceeds the speed of sound. A powder feed stock is injected into the gas stream, which accelerates the powder up to 800 m/s. The stream of hot gas and powder is directed towards the surface to be coated. The powder partially melts in the stream, and deposits upon the substrate. The resulting coating has low porosity and high bond strength.[1] Spray Coating