Common Questions about Air Filtration | Donaldson |

Q: Why am I experiencing short air filter

life?

A: The amount of dirt an air filter can hold before servicing

depends on many variables. The environment must be

considered (severe dust, soot, and moisture) as it is crucial

to know how much contaminant reaches the filter. This

depends on the severity of the environment and whether

the air cleaner is a one- or two-stage design. Another factor

is the size of the air cleaner and filter relative to the airflow

requirement. How long a filter lasts is largely a function of the

Original Equipment Manufacturer’s intake design.

Reference FMC TSB 89-3R3 and 06-2 for further details.

Q: What is the micron rating of my air

filter?

A: Typically, air cleaners and air filters are not assigned

a “micron rating.” Micron rating is a term used in liquid

filtration. Air filters are evaluated for efficiency using an

industry-wide standard ISO 5011. Efficiency is the percentage

of contaminant that a filter removes from the intake air

relative to its capacity.

Reference FMC TSB 04-3 for further details.

Q: What do inches or millimeters of H2O

have to do with an air cleaner?

A: In an intake filtration system the resistance to airflow is

called restriction. Restriction is typically measured in units

called inches or millimeters of H2O vacuum, and is defined as

the difference in static pressure between the atmosphere and

the outlet side of the system being measured. The higher the

restriction the harder an engine has to work to obtain clean

air for combustion. Engine manufacturers specify a restriction

level at which the air filter should be serviced.

Reference FMC TSB 89-3R3 for further details.

Q: Why do some air filters require U.L.

approval?

A: Some engine air filters utilize flame retardant filter media

to meet UL safety requirements. The U.L. rating covers

fire safety and backfire resistance aspects of industrial

trucks with internal-combustion engines, such as tractors,

platform-lift trucks, fork-lift trucks, and other specialized

vehicles for industrial use. These requirements do not cover

other possible safety aspects of such equipment. Additional

information can be found in UL 558 specification.

Q: Can you judge air filter service life by

visual inspection?

A: Visual inspection is not a recommended method for

determining an air filter’s service condition. Measuring intake

system restriction is the most reliable determination of

filter life. Service by restriction allows the filter to remain in

service until the maximum allowable restriction limit for the

application is reached. Various restriction indicating devices

are available for this purpose.

Reference FMC TSB 89-3R3 for further details.


Q: Why am I experiencing short air filter

life?

A: The amount of dirt an air filter can hold before servicing

depends on many variables. The environment must be

considered (severe dust, soot, and moisture) as it is crucial

to know how much contaminant reaches the filter. This

depends on the severity of the environment and whether

the air cleaner is a one- or two-stage design. Another factor

is the size of the air cleaner and filter relative to the airflow

requirement. How long a filter lasts is largely a function of the

Original Equipment Manufacturer’s intake design.

Reference FMC TSB 89-3R3 and 06-2 for further details.

Q: What is the micron rating of my air

filter?

A: Typically, air cleaners and air filters are not assigned

a “micron rating.” Micron rating is a term used in liquid

filtration. Air filters are evaluated for efficiency using an

industry-wide standard ISO 5011. Efficiency is the percentage

of contaminant that a filter removes from the intake air

relative to its capacity.

Reference FMC TSB 04-3 for further details.

Q: What do inches or millimeters of H2O

have to do with an air cleaner?

A: In an intake filtration system the resistance to airflow is

called restriction. Restriction is typically measured in units

called inches or millimeters of H2O vacuum, and is defined as

the difference in static pressure between the atmosphere and

the outlet side of the system being measured. The higher the

restriction the harder an engine has to work to obtain clean

air for combustion. Engine manufacturers specify a restriction

level at which the air filter should be serviced.

Reference FMC TSB 89-3R3 for further details.

Q: Why do some air filters require U.L.

approval?

A: Some engine air filters utilize flame retardant filter media

to meet UL safety requirements. The U.L. rating covers

fire safety and backfire resistance aspects of industrial

trucks with internal-combustion engines, such as tractors,

platform-lift trucks, fork-lift trucks, and other specialized

vehicles for industrial use. These requirements do not cover

other possible safety aspects of such equipment. Additional

information can be found in UL 558 specification.

Q: Can you judge air filter service life by

visual inspection?

A: Visual inspection is not a recommended method for

determining an air filter’s service condition. Measuring intake

system restriction is the most reliable determination of

filter life. Service by restriction allows the filter to remain in

service until the maximum allowable restriction limit for the

application is reached. Various restriction indicating devices

are available for this purpose.

Reference FMC TSB 89-3R3 for further details.