Takeoff & Estimating — Mechanical (HVAC)

HEPA Filter

A very high-efficiency air filter used where airborne particles must be controlled.

Quick Answer

A HEPA (high-efficiency particulate air) filter is a filter that can capture at least 99.97% of particles at 0.3 microns. It is used in cleanrooms, healthcare spaces, laboratories and abatement or construction containment. Estimators count HEPA housings and filters EA by size and add the fans, ductwork and testing around them.

The Full Picture

A HEPA filter is defined by performance. The EPA says a HEPA filter can theoretically remove at least 99.97% of particles at 0.3 microns, which is a worst-case size, and larger or smaller particles are captured at higher efficiency. The same definition appears in OSHA's asbestos rule, which describes a filter capable of trapping and retaining at least 99.97 percent at 0.3 micrometers. The EPA also notes that HEPA is common in portable air cleaners, and that ordinary furnace and HVAC filters are typically rated by MERV rather than HEPA.

In building work HEPA appears in three places. Cleanrooms, pharmacies and some laboratories use HEPA filters in the ceiling or in the air handler to control particles in the room. Healthcare facilities use them in certain isolation and procedure spaces. In construction and abatement, HEPA filtration is part of containment: OSHA's asbestos standard, 29 CFR 1926.1101, calls for HEPA-filtered vacuums, local exhaust and filtration devices serving negative pressure enclosures. The filters are usually temporary equipment in that case, not part of the permanent HVAC.

On the plans, permanent HEPA filters show up in the air handler or terminal housing schedules, on cleanroom ceiling plans and in the specification, normally Division 23 or a cleanroom section. The schedule lists the filter size, face velocity or airflow, efficiency and any pressure drop. Because a HEPA filter has high resistance to airflow, it raises fan size, motor power and duct pressure, which can change other equipment on the job.

The takeoff unit is EA by size and type: terminal HEPA housings, in-duct or bank housings, and the filters inside them. Pre-filters, gauges, seals, testing and certification are carried separately. Temporary HEPA units for containment are priced as rental or purchase plus operating time, and the duct or ventilation connection to the outside. Common errors are pricing the filter but not the housing, leaving out the field test after installation, and forgetting that replacement filters may be a turnover item.

Real Examples

→Worked takeoff: cleanroom ceiling: A reflected ceiling plan for a 12 ft by 18 ft room shows six terminal HEPA housings at 24 in by 24 in. The count is 6 EA housings and 6 EA filters, with six balancing dampers and six sets of duct connections. The estimator carries one field test line for the room and checks whether the schedule calls for pre-filters in the air handler.

→Temporary containment: A renovation in an occupied hospital wing calls for negative pressure containment. The estimator prices two portable HEPA air machines for the duration, the exhaust duct to the outside, the barrier and the monitoring, as part of the temporary controls and not as permanent HVAC.

→Fan impact: A laboratory air handler schedule lists a HEPA bank in the supply. The estimator confirms that the fan is sized for the extra pressure drop and carries the housing and the filters, since a HEPA bank changes both the equipment and the electrical load.

Common Misconceptions

People assume: Any filter labeled HEPA-type is a true HEPA filter.

Actually: True HEPA is a performance level, at least 99.97% at 0.3 microns. Products sold as HEPA-type or HEPA-like may not meet it, so the specification and the test report govern.

People assume: A HEPA filter can be dropped into any air handler.

Actually: It adds resistance to airflow, so the fan, the housing, the seals and the ductwork have to be designed for it. Fitting a filter into a unit not built for it can cut airflow.

Does MeltPlan Solve This?

Partially — adjacent

HEPA housings, filter banks and cleanroom ceiling modules are counted from the plans and schedules, and MeltPlan's takeoff service covers that counting work: AI pulls quantities from plans and US-based experienced estimators review and adjust them. Choosing the filter class, the containment approach and the testing scope stays with the engineer and your estimator.

Get filter housings and ceiling modules counted from your plans →

Frequently Asked Questions

What does HEPA stand for?

HEPA stands for high-efficiency particulate air. The term describes filters that capture at least 99.97% of particles at 0.3 microns.

Where are HEPA filters used in buildings?

They are used in cleanrooms, laboratories, some healthcare spaces and in temporary construction or abatement containment, as well as in portable air cleaners.

How are HEPA filters taken off?

Count the housings and the filters EA by size, then carry pre-filters, dampers, duct connections, gauges and field testing as separate lines. Temporary units are priced as rental or purchase.

Is a HEPA filter the same as a MERV filter?

No. MERV is a rating scale for general HVAC filters, while HEPA is a higher performance level. The EPA describes MERV as the usual rating for furnace and HVAC filters.