Illinois Food Cleanroom HVAC · October 8, 2026
Melrose Park: night fan speed is an octave band, not 55 dBA
You run a rooftop air handler over a food room in Melrose Park, houses are close, and someone handed you “section 15.24.080, 55 dBA at night.” We could not find that section in the village material we opened, and 55 dBA is the wrong unit for the state rule that does apply.
35 Ill. Adm. Code 901.102 limits sound to Class A land, which is where people live, by octave band. For a new source on Class C industrial land at night, the 125 Hz band is 62 dB, the 250 Hz band is 54 dB, and the 500 Hz band is 47 dB, measured at least 25 feet from the source. Existing sources are different: section 901.107(e) says the nighttime table in 901.102(b) does not apply to them, and they stay on the daytime table even at night. We read the Illinois Administrative Code text on October 8, 2026.
Chicago’s municipal code section 8-32-090 is the 55 dB(A) rule, measured at 100 feet or 70 dB(A) at 10 feet, and it names air handling units. Melrose Park has not published that section. The village’s 2023 code sheet adopts the 2021 International Mechanical Code and the Chicago electrical code. Adopting Chicago’s electrical book is not the same as adopting Chicago’s noise book. That mix-up is why this page exists.
- Do not turn the VFD down to hit 55 dBA unless you have measured the octave bands the state actually limits.
- A new nighttime source and an existing source use different columns. Ask which one you are before you buy a silencer.
- The village construction-hours ordinance, with fines of $50 to $750 a day, covers construction and alteration. It is not a permit to ignore 901.102 while the fan runs on Tuesday night.
| Who | Rule | What they measure |
|---|---|---|
| Illinois Pollution Control Board standards, enforced as state law | 35 Ill. Adm. Code 901.102 | Octave bands, at least 25 feet from the source |
| Village, on construction hours | Ordinance 959 and the permit handout | Clock time and whether the work is alteration |
| You and your balancer | Fan law: hertz versus static pressure | Whether the room still holds pressure after you slow the fan |
What the rule says here
The table is 35 Ill. Adm. Code 901, section 901.102. Daytime Class C to Class A starts at 75 dB in the 31.5 Hz band and 69 dB at 125 Hz. Nighttime Class C to Class A starts at 69 dB at 31.5 Hz and 62 dB at 125 Hz. Measurements are not taken closer than 25 feet to the property-line noise source. Nighttime for the related blasting section is described as 10:00 p.m. to 7:00 a.m. Use the part’s own definition of nighttime when you set the meter, and do not borrow a shift clock from a vendor.
Section 901.107(d) says the property-line tables do not apply to equipment being used for construction. That hole is where the village ordinance matters. The permit handout and Ordinance 959, amending the earlier construction section, prohibit construction or alteration from 7:00 p.m. to 7:00 a.m. on weekdays, from 5:00 p.m. to 8:00 a.m. on Saturday, and from 5:00 p.m. to 10:00 a.m. on Sunday and federal holidays. Sunday and holiday work outside those hours still may not come with loud or annoying noise, except an emergency cleared by the director of public works. The fine is not less than $50 and not more than $750 per day. Public improvements and public utilities are exempt. We read the permit PDF.
Chicago’s section 8-32-090 is the 55 dB(A) air-handler line. The September 2023 Melrose Park code sheet adopts IMC 2021 and the Chicago electrical code. It does not adopt 8-32-090.
If you skip it
Skip the octave-band reading and you will either trip a state limit you cannot see on a cheap dBA app, or you will throttle a supply fan until the packaging room loses the pressure you needed for the food. Both are expensive. The state rule does not care that the room is a cleanroom. A fan is a property-line noise source if it lands on Class A land.
A night crane is the construction ordinance, $50 to $750 a day. A night production fan is 901.102. Do not use one rule as a shield for the other.
How the next place differs
| Place | Published AHU number | What you use instead |
|---|---|---|
| Melrose Park | No 55 dBA section found | 35 Ill. Adm. Code 901.102 octave bands, plus construction hours |
| Chicago | 8-32-090: 55 dB(A) at 100 feet for mechanical stationary sources | Do not export it across the line |
| Elk Grove Village | No AHU decibel table in the sections we read | Zoning odor condition and the 2024 IMC |
Checklist for this job
Decide if the handler is an existing source. If it is, nighttime uses the daytime octave table under 901.107(e).
Measure at least 25 feet from the unit, on the receiving residential land, in octave bands. A phone dBA app is not the test.
Write the night hertz next to the static pressure in the packaging room. Slowing the fan is allowed only while the room still meets its own pressure design.
If you are rigging a new unit, stay inside the village construction clock or get the emergency permission the ordinance describes.
Do not put “55 dBA, section 15.24.080” on a submittal. That cite did not survive a reading of the village sheets we opened.
Filter bypass and odor at Elk Grove are a different note.
Fee or timeline in the document
The village noise documents we read do not charge a 10-business-day acoustic review fee. They charge a fine for construction-hour violations: not less than $50 and not more than $750 per offense, each day separate. There is no published fee for “night VFD approval.” If a building permit is required to change the unit, the fee is on the building schedule, which this page did not copy because we did not have that table.
State enforcement of 901.102 is not a village invoice either. Budget the measurement, not a fictional filing fee. The food-room diagnostic, if you still need pressure and filter readings after the fan slows, is the scope on the rule page.
Questions people type
The limit we can cite is the Illinois octave-band table in 35 Ill. Adm. Code 901.102, not a village 55 dBA line. A new Class C source at night, received on Class A land, is 62 dB in the 125 Hz band and 54 dB in the 250 Hz band, among the other bands, measured at least 25 feet from the source. Existing sources stay on the daytime table at night.
You cannot promise both from a hertz number alone. Dropping frequency drops fan pressure with it. Measure the room-to-corridor differential after the change. If the room sags, you need a silencer, a barrier, or a different fan, not another 5 Hz. The state rule does not grant a cleanroom exception.
We did not find that section in the village zoning pages or the 2023 code sheet. Do not build a compliance file on it. Use 901.102 for the operating fan and the construction-hours ordinance for the crane.
Section 8-32-090 is a Chicago section. It limits mechanical stationary sources, including air handling units, to 55 dB(A) at 100 feet. Melrose Park’s published code list adopts a Chicago electrical code and an IMC. It does not, in the sheet we read, adopt 8-32-090. Using the Chicago number in Melrose Park will aim your fan at the wrong test.
Related
References
- Illinois Administrative Code. “35 Ill. Adm. Code 901,” sections 901.102 and 901.107. Accessed October 8, 2026. www.ilga.gov/agencies/JCAR/EntirePart?titlepart=
- Village of Melrose Park. Permit handout stating construction hours and the $50 to $750 fine. Accessed October 8, 2026. www.melrosepark.org/wp-content/uploads/2020/10/P
- Village of Melrose Park. “All applicable codes,” September 2023, listing IMC 2021 and the Chicago electrical code. Accessed October 8, 2026. www.melrosepark.org/wp-content/uploads/2023/09/V
- City of Chicago. Municipal code section 8-32-090, mechanical stationary sources. Accessed October 8, 2026. Cited only as the neighboring city’s rule. codelibrary.amlegal.com/codes/chicago/latest/chi
How to cite this page
Illinois Food Cleanroom HVAC. (2026). Melrose Park: night fan speed is an octave band, not 55 dBA. https://illinoisfoodcleanr.xyz/melrose-park-food-processing-air-handler
Byline: Illinois Food Cleanroom HVAC.