FAQs

What is the proper way to get an even finish when painting a metallic hood without getting the stripe effect when applying the clearcoat?

What is the proper way to get an even finish when painting a metallic hood without getting the stripe effect when applying the clearcoat?

Finish Application If the stripping is happening only after you start applying the clear coat it is possible that the basecoat is not completely flashed off when the clear in applied. This can cause the metallic to shift. Another possibility is that the basecoat has […]

How many air changes are required for a 16 by 14 by 40 paint booth?

How many air changes are required for a 16 by 14 by 40 paint booth?

Air Changes There is no code or standard that requires a specific air change for paint spray booths. It is more common for the ventilation performance of a spray booth to be specified by the average velocity through the booth or in the vicinity of […]

What is the best placement of sensor tubes coming from the magnahelic gauge for a downdraft paint booth?

What is the best placement of sensor tubes coming from the magnahelic gauge for a downdraft paint booth?

Measuring Pressure

The answer depends on what pressure differential you are trying to measure. If you are measuring cabin pressure compared to building pressure, the high-pressure sensor tube should be mounted in the cabin away from any booth openings. The low-pressure tube should be left open to the shop.

If you want to measure static pressure loss across the pit filter, the high-pressure sensor tube should be mounted in the cabin away from any booth openings, and the low-pressure sensor a few inches below the pit filters.

Are manometers or other pressure drop devices required by law on exhaust filters?

Are manometers or other pressure drop devices required by law on exhaust filters?

National Fire Protection Association A means is required to make sure that you are moving the required amount of air for paint spraying. Your choices depend upon the code or standard adopted by your local authority. If NFPA 1 Fire Code is being enforced then […]

What are the potential hazards when painting with the doors open?

What are the potential hazards when painting with the doors open?

“We are using a spray gun between 20-60 psi when the production doors are open on the unit. Do the filters on the doors provide a significant protection factor when dealing with Isocyanates?” The paint booth should have the doors closed during paint spraying. The […]

How do I maintain a specific spray temperature inside the paint booth?

How do I maintain a specific spray temperature inside the paint booth?

I live in Malaysia with the temperature of 32 degree Celsius, how do I maintain the spray temperature of 23 degrees Celsius inside the painting booth? Do I need to install a chiller and humidifier?

Due to the conditions in Malaysia the temperature set-point being asked for is at or below the dew point in the summer months. A chiller would be required to attain that temperature, but the outside walls of the booth may form condensate if the dew point of the outside air is at or above 23°C.

Humidity is a large issue in Kuala Lumpur, Malaysia. Cooling the air would cause for other conditions such as condensate on the booth walls or a high relative humidity in the booth since the air is being cooled down to the saturation temperatures in the summertime.

Standard design practice would be to condense the moisture out of the air by sub-cooling with a chiller and then reheating the air with indirect heat to the desired operating temperature and relative humidity set-point. This practice would be done only with the use of an insulated booth with a vapor barrier in the environment of Malaysia.

Is there a “magic number” on the manometer at which paint booth filters should be changed?

Is there a “magic number” on the manometer at which paint booth filters should be changed?

Regardless of the filter used, it is a matter of how much total resistance is designed into the fan in question and the relative condition of the fan. All fan units are designed to operate within a range of resistance, that includes the ductwork, plenum […]

Is there a minimum airflow guideline for non-spraying times?

Is there a minimum airflow guideline for non-spraying times?

We would like to turn down the airflow in our spray booth during non-spraying times (i.e. warming it up in the morning). There is no specific airflow requirement for non-spraying modes such as prep or unoccupied times. Generally, users will revert back to standard building […]

What are the code requirements for negative/positive pressure in a paint spray booth?

What are the code requirements for negative/positive pressure in a paint spray booth?

Code Compliance:

Only one of the standards (EPA’s 6H Rule) that we see applied to spray booths addresses booth pressure specifically. One of the purposes of a spray booth is to confine and capture the overspray. While the spray booth’s ability to do this may be directly related to booth pressure, the standards for spray booth typically describe performance requirements and not specific values of pressure or velocity (with the exception of the IFC). The type of booth will have an impact on the pressure needed in the spray booth to achieve the performance required by the industry standards. The following is a summary of the statements in the various codes that address this issue.

National Fire Protection Association:

NFPA 33 Standard for Spray Application Using Flammable or Combustible Materials is the principal standard for spray booths. The IFC and OSHA codes are based upon the requirements of NFPA 33. NFPA 33 requires that “Each spray area shall be provided with mechanical ventilation that is capable of confining and removing vapors and mists to a safe location and is capable of confining and controlling combustible residues, dust, and deposits. The concentration of the vapors and mists in the exhaust stream of the ventilation system shall not exceed 25 percent of the lower flammable limit.” It also states that “Spray areas equipped with overspray collection filters shall have an effective means to ensure that the performance requirements of Section 7.2 are met.” Acceptable means to comply with this requirement include visible gauges, audible alarms, approved interlocks, or an effective inspection program.

International Fire Code: Chapter 15

The International Fire Code (IFC) does not specifically state a booth pressure requirement. It does state that “Mechanical ventilation shall be kept in operation at all times while spraying operations are being conducted and for a sufficient time thereafter to allow vapors from drying coated articles and finishing material residue to be exhausted. Spraying equipment shall be interlocked with the ventilation of the flammable vapor areas such that spraying operations cannot be conducted unless the ventilation system is in operation.” The IFC also adds the requirement that “Ventilation systems shall be designed, installed and maintained such that the average air velocity over the open face of the booth, or booth cross section in the direction of airflow during spraying operations, shall not be less than 100 feet per minute (0.51 m/s).”

OSHA 1910.107:

OHSA also does not state a booth pressure requirement, but like the IFC requires that “All spraying areas shall be provided with mechanical ventilation adequate to remove flammable vapors, mists, or powders to a safe location and to confine and control combustible residues so that life is not endangered. Mechanical ventilation shall be kept in operation at all times while spraying operations are being conducted and for a sufficient time thereafter to allow vapors from drying coated articles and drying finishing material residue to be exhausted.”

Environmental Protection Agency (EPA):

The EPA is primarily concerned with outdoor air quality and lets other industry standards and OSHA address life safety issues (fire hazards, personnel exposure, etc), but in their 6H rule they allow for fully enclosed booths (no openings, adequate seals round doors) with an automatic pressure balancing system to operate at positive pressures up to 0.05 inches water gauge.

What are the pros and cons of semi-downdraft and crossflow booths?

What are the pros and cons of semi-downdraft and crossflow booths?

I’m considering installing a new paint booth at my facility. I have the option between a semi-downdraft booth (equipment is to heavy for a down draft type booth to support) and a crossflow booth. I was wondering what the pros and cons are to each […]