While buying a car do we care what engine it will have and if we are able easily, fast and safety to make an overtake manoeuvre on our crowdy roads? Is it important if the car has an air condition or a power steering?
Let us unswer the question: while making such a serious decission is it only the price that matters or is it also important what do we get for this price?
Remember that spray booths watched from outside hardly have any difference and we have to make a decission if we buy it to bring jealousy with the owners of the neighbour garage or we buy it to assure a stable and safe working conditions for our sprayer.
We understand that this is a very difficult decission that is why we have prepared this guide.

Before we talk start technical topics, we would like mention the possibility of buying second handed pain booths brought from west countires.
Could we go to the Casino and play "red" or "black" alternatively "even" or "odd" for the abount of about 40.000 zł? If the answer is - yes, I?. Gratulate you a bent for gambling and rich wallet. In this case money is the only loss. In case of the spray booth it is not only money but sometimes also somebody's health or life. In the year 2001 there were explisions and fires in several spray booths in Poland.
There have been tighten rules concerning spray booth work parameters in European Union and a big amount of them is now brought to our country.

Please do remember that Poland is the country, which aspirates to be a member of EU and weather we want it or not all Union directives will be in force also in our country.

The basic parameter is spray booth's dimansions because they determinate the size of vehicles. It would be difficoult to work in the 5m length spray booth if the car is 4m long. That is why most of the spray booths have the length of 6 - 7 m and 4m width. This width is optimal and adapted to most of vehicles.
Everybody knows that is would be more comfortable to work in a 5m long spray booth. We should also understand that increasing a spray booth surface will bring the increase of ventilation system efficiency to assure a proper air flow speed. This will also increase the use of heating system that is neccesary to assure a proper level of thermal jump ΔT These factors cause the increase of exploit costs. Like you can see there are no technical obstacles to make a long and wild spray booth but there are high execution and exploit costs.

There are no limits concerning the height of the spray booth. The higher it can be, more comfortable it is to work. The spray booth that is 3m high is much more comfortable that 2,6m because it can also serve trucks and buses. Increased height has no impact on neccesity of bringing more efficient generator.

The following parameter that characterize spray booths is ventilator's efficiency. It must be selected to achieve at least an average value of 0,25 m/sec by a vertical air move (air flow speed). It means that the air together with a spray mist moves by the vertical move up and down 25cm/sec. After placing a vehicle in a spray booth the active spray booth surface decrease and flow speed rise in proportion to the surface decrease. Air flow speed depends on two factors: spray booth surface and used ventilators efficiency. German, French or Belgian spray booth producers use in their products exactly 0,25 m/sec flow speed and most of Italian or Spanish producers use 0,20 m/sec flow speed.

The problem is with the reliability of technical details given by producers, especially concerning ventilator's efficiency that is different depending on achieved pressure. Some producers give the values according to ventilators that are working without a load that means maximum values or with channels and filters resistance that means nominal values.

There is one more thing connected to the ventlator's efficiency and that is an environmental protection. There is The Highest Permissible Concentration of damaging substance excreted by a spray booth. While one hour of spraying no matter if in garage or spray booth the same amount of lacquer material is released from the pistol. Ventilator's efficiency depend on the level of diluting excreted dangerous and harmful substances.

Ventiolator's efficiency is connected to the spray booth surface, air flow speed and also ecological and safe work of the whole spray booth.

Correctly configurated spray booth must be equipped in a separate fan system both ventilation and blow away. The fact that in Poland 80% of spray booths have only ventilation fan system is caused only by buyer's unknowledge, sellers abilities and costs.

There is a heating system straight connected the ventilation system. It must be selected according to the device efficiency to assure a proper temperature increase (thermal jump ΔT) on the same level that the climate in assembled spray booth room. Thermal jump is an air temperature increase and that is the difference between the air sucked in to the spray booth (almost always form outside) and a maximum air temperature deliviered to the inside of the spray booth after passing a heating system. If there is winter and the outside temperature is -15^oC, and if the optimal temeprature in tha spray booth we want to achieve is 20^oC we must achieve a thermal jump on the level of 35^oC. However the heating efficiency (power) will be different for various ventilator's efficiency.

Technically it does not cause any problems. It is possible to install as big heating system to achieve a problem thermal jump without any difficulties. We should think if in our climate conditions where we have about 7 days a year the temperature below -15^oCthe use of a huge heating system is really neccesary. Maybe we should install less efficient heating system that will not be able to work in very low temperatures but for the rest 95% of days in a year it will work with its full power.

The most profitable solution in Polosh climate is the use of the heating system that achieve a thermal jump on the level of 26 - 27^oC connected to a special system that lets to increase temporary ΔT to about 35^oC. This kind of solutions are used by some of famous spray booth producers and find application in spray booths utilized in north countries (especially Scandinavia). It is the most rational solution of heating system efficiency.

One of the most important element for a proper system work is its foundation. The best solution is so-called concrete moat. It is a lower air flow channel adequately shaped and with an adequate depth. It assures unlimited and even air flow. All traders will talk about problems concerning building this moat (made by an investor) and will suggest much easier solution like a metal base. Because of a small height (about 300 mm) of a metal base it will be a kind of a barrier for a proper air flow in it. Metal base is only a replacable solution also in famous companies in places where because of technical reasons it is not possible to make a concrete moat. In spite of all a metal base is not so cheap.
Once again we have a chance to think why we have decided to buy a spray booth?

Ważnym parametrem jest również ilość, rozmieszczenie, rodzaj i barwa oświetlenia. Człowiek pracujący w kabinie lakierniczej musi mieć możliwość łatwego rozpoznawania i porównywania barw w związku z czym powinny być zastosowane świetlówki o odpowiednio dobranej barwie emitowanego światła, lampy muszą mieć odpowiednią klasę ochrony jeżeli dostęp do świetlówek odbywa się od strony wewnętrznej, dla zapewnienia odpowiedniej jasności pomieszczenia kabiny konieczne jest zastosowanie odpowiednio dużej ilości punktów świetlnych.

The quantity, place, type and colour of the lightning are also very important elements. A person that works in a spray booth must have a possibility of identifying and comparing colours. That is why fluorescent light with a specially selected colours of emitted light is neccesary. Lamps need a proper security class if the access to the fluorescent light is from the internal side. To ensure a proper spray booth room brightness it is necessary to use enough amount of light points.

There are two ways of placing lamps in the spray booth. First is placing lamps on the slants between the spray booth wall and filter ceiling. It causes a higher light intensity in a work place and less quantity of installed lamps and fluorescent lights. In case of installing only a ventilation system the increased susceptability for turbulences and air whirl becomes a disadvantage. Second way is placing a big amount of lamps in wall pannels, mostly in two lines. This solution gives opportunity to install ceiling filters with almost the same surface like a spray booth surface. The disadvantage is a double amount of the fluorescent light and much higher electricity use. This solution gives a very good distract and high light intensity in the spray booth.
The next question is: cheap or good?

A middle solution with a very good parameters is placing lamps on the top of slants and additional vertical lamps in the corners of the spray booth on the floor level. It gives a good intensity in a working area and does not make a shadow on the surface of the sprayer's shadow. All the lights glasses must be made from the safe glass.

A spray booth is mostly made from pannels self-supporting construction, isolated by different materials, like: polystyrene, frothen poliuretan, standard or ironed mineral wool.
Imagine an expirience.

We put on one table: a piece of polystyrene, poliuretan and a piece of a mineral wool. We will play with a lighter and see what will be the result of the play. Lets take a spoon of a solvent used in spray booths that is a part of a lacquer and pour on each of prepared materials. After this kind of expirience we will already know what kind of isolation should be used in spray booth's constructions.

WMost of the producers isolate only sprayh booth's walls. Famous producers also isolate roofs or even whole generators where the air with a temperature of 60^o C. flows in a drying phase. There are also rumours that no isolation is necessary and this kind of spray booths arrive to Poland. Imagine a late autumn and cold outside. In a holl shop is the temperature of 15^oC . There is a recently sprayed car in a spray booth. The temperature inside the spray booth is 60^oC. It means that the temperature difference is 45^oC. Let's unswer the question if there is a heat penetration throught a spray booth's wall that is made from 1 mm metal steel.

The next thing that have a great impact on a device efficiency is the floor bars size under which spray-stop floor filters are placed. There are several solutions from the worst to the best.

Narrow bars under a car - a little bit archaic solution in the cheapest spray booths with a small ventilation system. A car surface blocks an air access to the outflow channels.

Two narrow bars placed under car wheels - more efficient solution because parts of bars can be seen from the car side contour. It lets for a better air penetration to the outflow chanel.

Two narrow bars placed under car wheels connected to additional bars at the beginning and the end of the channel, so called "RING" system - solution similar to the previous but giving more efficient air flow also in the front and the back of the vehicle. It increases the result of an air fall and make a good spraying of those parts to be possible.

Above solutions require a central precise car placing to make an air fall to be maximum even. This kind of solutions dominates in devices with small efficiency ventilators (mostly one ventilator systems). The less floor filter's sufrace is the easier and faster the result is achieved. Regardless of the filters surface while spraying the same amount of spray lacquer is released and that is why the amount of particles is also constant and the small surface filter will get easily clogged. The consequence of the floor filter pollution is a high increase (especially in one ventilator spray booths) of hypertension in the spray booth that leads to air fall speed decrase.

If this value increases below 0,16 m/sec we will achieve somillar conditions to the conditionas in the garage with opened widnows.

A floor grated on a big surface, mostly 5 x 3 m - very efficient solution, deprived all above mentioned faults.

A floor grated in 100% - the best and the most expensive solution because of the big amount of platform grating and neccessity of making supports systems on which gratings are hanged.

ATTENTION - some of producers use two last solutions but still under grating and filters they put metal sheet on the surface of floor grating leaving only two narrow bars under the car wheels. This kind of solution is caused by using small efficiency ventilators.

ENTERING door to the spray booth - there are also differences in the way of making entering door. The entrance must make an easy entering to be possible and after closing such a sealing that no air with harmfull and dangerous substances would get out. There are two basic ways of making doors. First - double wings door, second - treble wings door. Treble wings door take less place while opening because of the narrow door. One of the door wings works as a service and must be equipped in a safety lock which lets to open the door under a pressure form inside in case of any crisis situation. When applying double wings door it is necessary to install a separate service door. Every construction should include circuital gasket and closing system, eg. bolting to ensure a proper door fram tightening. It is also godd if door wings are thermally isolated.
The maximum height and width is an advantage because it ensures a trouble-free entering to the chamber.

The way of working in a spraying phase should be the same for the sake of safety and efficient ventilation. An injection ventilator take a clean air from outside and point it to the heat exchanger. There the air is heated and pointed to the spray booth filtering joint assembly. Then it goes through ceiling filters and penetrate with a vertical move up and down depending on the spray booth equipment. It can also be "squeezed" through crates and floor filters and pushed out to the mouth ventilation channel placed over the roof of the building (one-fan demister spray booths). It can also be drawn in by an extracting ventilator and pushed out through a mouth ventilation channel over its buildings (double-fan demister extracting spray booths). The air is deeply polluted that is why it can not be used in spray booth heating.

In drying phase individual devices work in different ways. It is caused by a neccessity of achieving much higher temperature 60-70^oC. The temperatre on the level of 70-80^oC will not be able to achieve while using a heating system with a stantard heating efficiency.

One of the solutions would be installing a heating unit with a hudge power but it is economically not justified. There are three solutions to the problem right now.
The simpliest technical solution is to let only 20-25% of the initial ventilator efficiency value to flow through the heating exchanger. This amount of the air can be easily heated to the demanded temperature. The disadvantage is a very irregular drying of a vehicle. Vertical parts of the car body dry up much longer then a horizontal parts and the process of drying may be very long. In this solution the whole heated air is thrown to the atmosphere.
Other solution is a mechanical limitation of the inlet channel section that decreases the efficiency of ventilators to about 50%. Additionally there opens a cover between the inlet channel and the heat exchanger chamber that lets to suck in some amount of hot air through the air stream that is suck in by inlets. The air delivered to the heat exchanger is mixed with the hot air and that is why its temperature is much higher. It causes that the air that flows through the heat exchanger can achieve a proper temperature increase. Pople who are connected with spray booths production call his solution "a by pass". The advantage of it is delivering much bigger of the hot air what incredibly improves and accelerates a drying process. Like in the previous solution a hot air is evaporating to the atmosphere.

Next solution is a system, which causes that 90% of the air mass circulates in the closed circulation. It is caused by a system with covers that automatically close inlets and open the connection of a demister ventilator with moat. A ventilator sucks in a previously warmed air from a spray booth and again directs it to the spray booth through the heat exchanger where the temperature falls are suplemented. A cover that closes an inlet is specially leaky to assure 10% of fresh air that is necessary for the dry process. Until recently while this phaze an extracting ventilator was off and 10% of the air excess were gravitationally excreted. Directives of the EU has changed in this range and now to help in excreting 10% of this air an extracting ventilator must work also in the drying phase.

Which solution is the best for our customer? Lets use an example again. Lets imagine that we drive a car with 4 people. There is a winter and it is freezing outside. We drive several kilometers and the engine achieved a proper temperature. The driver put on the heating and the ventilator on the lowest revolution. Will people sitting in the back feel warm? After what time?
And what will happen if a ventilator will be on the highest revolution? Will the heat appear faster?
Spray booths are much more technically comlicated, equipped in the electronic steering systems can also have an additional working functions:
- ventilation phase, after a spraying phase
- chilling phase that turns on automatically after the drying process
- special saving thermal energy system, which switch the spray booth automatically into a recirculation phase in case we stop the spraying process.
- Damages visualization system that is given in the form of codes on the controller
- Possibility of installing completely automatic hypertension regulation that is in the spray booth. That means to ensure always the same air flow speed.

Let us go back at the end to the main point of the spray booth that is ventilation and heating unit called a generator or an aggregate.

Producers use as always different solutions based on technical possibilities and mostly costs of production. In most of cases this kind of generator is built as a self-supporting construction made from steel sheet metal addequately bended to achieve a space profiles, connected on the place of assembly by rivets or sheet metal selt drilling screws and fulfilled by covers made from sheet metal. Individual parts of construction are connected and form a carrying structure for the heat exchanger, ventilator(s) and additional equipment, like: recirculation cover (if occurs), pneumatic motor operators, servo-motors, support for inlet and launcher ventilation channels and other parts that may occur in different constructions.

Producers with a good reputation are companies with sereval years tradition that do not specialize in making mass products. These companies always make controls of assembly and the correctness of activity. Their generators are built on the basie of solit steel constructions, able to carry big load. It is delicered to the receiver in the form of ready to work units, which incude all necessary elements inside, like: ventilators, engines, covers, heating exchanger etc. It brings several probles connected with transportation and unloading of those devices.
The most essential parts of the generator are ventilators and heating exchanger.

Heating exchanger is necessary to "mediate" between a burner flame and the air given to the spray chamber. A burner placed on the exchanger's wall has a flame directed to the inside of the exchanger, to the burning chamber. Fumes are piped away to the fumes chiminey through the flame channels. The air is given through the demister ventilator and heats from the exchanger.
Most of the producers make exchangers with a simple construction, with fume channels made in the shape of vertical cracks place side by side in one line over the burning chamber. In this kind of the exchanger the air goes through those craks in not disturbing way.
Other constructions place over the burning chamber a rounded flame pipes placed in several lines. In this kind of exchangers a flowing air must make a "snake" move. This cause that the exchange surface is very big.
In heating systems of spray booths there are oil or gas burners. It is good if burners are from a famous producer that could make a proper tests of the product. Burner's power must be adjusted to the required powoe of the heating system.
A consumption of the fuel depends on the burner's power and on the work intensivity. That means that of there is cold outside, a burner must work longer to make the air get a proper temperature. If it works longer, it uses more fuel. That is why it is installed.
In spray booths heating systems one can come accross a following oil and gas burners:

One step - mostly used. The disadvantade is the big +/- difference, even 3-4^oC while a spraying phase. After setting a temperature of 20^oC) is sprays part of the car in 17^oC and in the minute another part of the car in 23^oC, A lacquer in this conditions will have a different stick.

Double step - if they have installed a proper (eg. Spraytronic) steering element, they are almost out of above mentioned faults. Depending on the heat demand, first or both steps of the burner are working.
Gas burners can also have so called a unit flame system. This is a very expensive solution, but assuring a stable temperature.

Used in spray booths ventilators are:
- One stream, placed directly on the engine axle,
- Double stream , driven by a transmission belt.
These are always ray ventilators.
One stream ventilators are good and cheap solution. They stand a high ceiling filters pollution. They do not require any regulations, have no rotary speed regulation possibility and also efficiency because it is the same as the engine rotary.