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New Hampshire Department of Environmental Services

Frequently Asked Questions
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  • Who is subject to Env-A 1400?
    Env-A 1400 applies to: " the owner of any new, modified, or existing stationary source, area source or device which emits a regulated toxic air pollutant into the ambient air, unless exempted under Env-A 1402.01, Env-A 1402.02 or Env-A 1402.03." (Env-A 1401.02).
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  • Are regulated toxic air pollutant (RTAP) emissions from ALL activities at a facility subject to Env-A 1400?"
    No. Emissions of RTAPs from activities listed in Env-A1402 are exempt. In addition, NHDES policy exempts activities that are otherwise determined to be "negligible." "Negligible" activities are defined as those that meet all of the following key criteria.
    • The activity is not considered a "primary" activity. (A primary activity is an activity that is integral to the principal business activities of the facility).
    • The activity does not result in actual emissions of any RTAP greater than the established de minimis level for that RTAP.
    • The total actual emissions of the RTAP from all insignificant activities at the facility are less than the established de minimis level for that RTAP.

If all three of the conditions above are met, then the activities will be considered "negligible," and will not be required to be included in the Env-A 1400 compliance determination. Please note, however, that although a "negligible" activity is not required to be included in the facility RTAP emissions, some records (such as purchase records, material use, etc.) must still be kept in order to verify the "negligible" status of the activity as it applies to Env-A 1400.

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  • Do I use "actual" or "potential" emissions to demonstrate compliance?
    NHDES has adopted a policy that allows sources of regulated toxic air pollutants (RTAPs) to use actual, uncontrolled rather than potential emissions to demonstrate compliance with Env-A 1400 provided they meet one of the provisions listed below.
    • Actual emissions of RTAPs are demonstrated to be below the established de minimis emission levels.
    • Using the in-stack concentration method (Env-A 1405.04), the actual adjusted in-stack concentrations of RTAPs are demonstrated to be less than 50 percent of the established ambient air limits (AALs).
    • The results of a dispersion modeling analysis show that the actual emissions of RTAPs result in a predicted, ambient air impact beyond the compliance boundary of less than 50 percent of the established AALs.

The attached flow chart Adobe Acrobat Reader Symbol illustrates the process of determining whether actual or potential emissions should be used for demonstrating compliance with Env-A 1400.

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  • Diagram of an unobstructed stack showing the top of the stack at least two feet above the roof line and at least ten feet away from the highest part of the roof.How do I know if my stack is unobstructed?
    A stack is considered unobstructed if there is no impediment to vertical flow and the exhaust stack extends at least 2 feet higher than any roofline within 10 feet of the exhaust stack measured horizontally.
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  • I have a used (waste) oil furnace. Is it exempt from Env-A 1400?
    No. Used oil is not a virgin petroleum product and therefore emissions from its combustion as a fuel are subject to Env-A 1400. However, NHDES has determined that in most cases emissions from small, used oil furnace installations do comply with the Env-A 1400 requirements.

NHDES has conducted a study of typical recycled oil burner emissions in order to simplify the compliance determination process. The study examined RTAP emissions from typical recycled oil burners using a variety of recycled oil characteristics, fuel use rates, and installation configurations. The results of this study show that recycled oil burners are in compliance with the provisions of Env-A 1400 provided they meet all of the following criteria.

    • The sum of all units are rated at 500,000 Btu per hour or less heat input.
    • The sum of all units are rated at 3.6 gallons per hour or less of fuel use.
    • All units burn 8,640 gallons per year or less of waste oil.
    • Each exhaust stack is 8 inches or less inside diameter.
    • Each exhaust stack outlet is 20 feet or more above the ground.
    • Each exhaust stack is vertical and unobstructed.
    • All units are operated and maintained in accordance with manufacturer's specifications.

If your facility operates recycled oil burners meeting all of the above criteria, NHDES has determined that its emissions are in compliance with Env-A 1400 and the unit would be exempt from Env-A 1400. However, records such as annual fuel use, number of days of operation, and maintenance records must be kept on-site to document that the above criteria are being met. Owners/operators of recycled oil burners that do not meet all of the criteria listed above should contact NHDES and conduct a source specific compliance determination as soon as possible in order to verify the compliance status of the installation.

All used oil burners, regardless of their compliance status with the NH Air Toxics Control Program, are required to submit a Notification Form to the NHDES Waste Management Division, (603) 271-2921.

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  • If I need to have a dispersion modeling analysis of my regulated toxic air pollutant (RTAP) emissions done, who can do it for me?
    NHDES Air Resources Division will conduct a dispersion modeling analysis for any affected New Hampshire source for a fee of $1,500. However, sources are not precluded from using a qualified consultant using NHDES approved methods to conduct dispersion modeling if they choose. In order to conduct the dispersion modeling analysis, site-specific information such as local topography, property boundaries, building heights, stack heights, stack velocity and RTAP emission rates must be provided.
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  • Is stack testing required for emissions determinations?
    No. While a source may choose to conduct stack testing to determine RTAP emissions, it is not required. Other methods such as the use of engineering calculations, published emission factors, etc., may be adequate. If you choose to conduct stack testing to determine RTAP emissions, you should send NHDES a description of the proposed test methods, procedures, operating parameters and proposed test date prior to conducting the test, and request NHDES approval.
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  • My facility has a wastewater evaporator. Do I need to show compliance with Env-A 1400?
    Yes. You will need to make sure that the emissions from the evaporator are in compliance with Env-A 1400. However, it is important to remember that compliance with Env-A 1400 only applies to RTAPs that can be emitted into the outdoor air. RTAPs that are not volatile, including most metals, and are retained in the wastewater are not emitted, and are exempt from Env-A 1400. On the other hand, any volatile RTAPs (e.g., solvents) in the wastewater can be emitted by an evaporator into the outdoor air. As a result, compliance with Env-A 1400 for these RTAPs must be demonstrated, and appropriate documentation of compliance must be retained on site. All wastewater evaporators, regardless of their compliance status with the NH Air Toxics Control Program, must determine their need for a Limited Permit under the Hazardous Waste rules. Information on the requirements for a Limited Permit can be found on the Hazardous Waste Management Bureau > Frequently Asked Questions or by contacting Zachary Lorch of the Hazardous Waste Management Bureau at (603) 271-5328 or via e-mail at
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  • My process generates a particulate dust that is on the list of regulated toxic air pollutants (RTAPs). Do I base my Env-A 1400 compliance determination on the total amount of dust emitted?
    In most cases, only the "respirable" fraction of particulate RTAP emissions should be considered. Generally, "respirable" particulates will be considered to be that fraction of particles with a median aerodynamic diameter of less than ten microns (PM10). If your RTAP emissions include particulate dusts, please consult with NHDES to confirm that only the respirable RTAP fraction requires consideration, and to determine what portion of emitted dusts are considered respirable.
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  • Results of dispersion modeling show that my maximum impact area is within the facility boundaries. Do I have to show compliance with the ambient air limits (AALs) on the facility property?
    Env-A 1400 is intended to address the exposure of the general public to toxic air contaminants and therefore technically applies only to off-site ambient air impacts. Worker exposures to toxic air contaminants on-site are generally covered by applicable OSHA regulations. Therefore, unless the general public has open access to the facility property, on-site impacts are not covered by Env-A 1400. Although not required, NHDES recommends that the ambient air limits (AALs) established in Env-A 1400 be considered when addressing on-site air impacts.
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  • What do I need to do to comply with Env-A 1400?
    Each affected source must demonstrate that its uncontrolled emissions of regulated toxic air pollutants (RTAPs) do not impact the off-site ambient air above the ambient air limits (AALs) established in the rule using one of the three methods described in Env-A 1405. Affected sources that can demonstrate compliance must maintain documentation on site to verify compliance status. All sources were required to be in compliance by May 8, 2001, and new sources must be in compliance at startup.
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  • What if my modeled regulated toxic air pollutant (RTAP) emissions exceed the ambient air limits (AALs)?
    If an affected stationary source cannot demonstrate that its uncontrolled emissions are in compliance with the applicable AALs, then it is required to obtain a permit limiting the impact of its emissions to levels below the established AALs, e.g., production limits, limits on hours of operation, control device requirements, etc. These sources were required to obtain a permit from NHDES and be in compliance with Env-A 1400 prior to May 8, 2001. New sources subject to Env-A 1400 must file a permit application prior to start up.
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  • What records do I need to keep?
    All sources subject to Env-A 1400 are required to maintain documentation on site that demonstrates that the facility is in compliance with the regulated toxic air pollutant (RTAP) ambient air limits (AALs). These records shall be retained and made available to NHDES upon request or in the event of an inspection. These recordkeeping requirements are not prescriptive and will vary according to factors such as the method of demonstrating compliance (de minimis emission level method, in-stack concentration method, or air dispersion modeling analysis) and process type, on a case-by-case basis.

The goal is for these records to verify compliance of emissions of RTAPs from the facility for both the 24-hour and annual AALs

Records may vary from direct verification records (such as continuous emissions monitoring) to indirect verification methods (such as material application rates and safety data sheets, or process feed rates and published process emission factors). Although not required, it is recommended that affected facilities contact NHDES for review of the proposed recordkeeping program prior to its implementation.

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  • Which activities are exempt from Env-A 1400?
    If your business uses chemicals in its manufacturing or business process listed in the table in the NH Air Toxics Rule, you may be subject to the rule, and you must determine your compliance status. The following are some activities that are exempt from the rule:
    • Mobile sources
    • Normal agricultural operations
    • The application of a regulated pesticide
    • The combustion of one or more of the following fuels:
      • Coal
      • Natural gas
      • Biomass as defined in Env-A 1401.03 (d)
      • Virgin petroleum products
      • Propane
      • Bio-fuel as defined in Env-A 1401.03 (c)
  • Regulated gasoline dispensing or storage facilities or cargo trucks
  • Crematoriums
  • Certain publicly owned wastewater treatment facilities as defined in Env-A 1402.02(j)
  • Certain major stationary sources that are subject to federal regulations as defined in Env-A 1402.03
  • Regulated open burning
  • A pneumatic transfer system for collecting sander dust which uses a baghouse that is operated and maintained in accordance with the manufacturer's specifications
  • Wastewater evaporators that do not process wastewater containing volatile organic compounds (VOCs)
  • Used oil heaters that meet the criteria in Env-A 1402.02 (g)
  • Automotive finishing operations that meet the criteria in Env-A 1402.02(m)
  • Solvent cleaning of parts performed exclusively by hand wiping or hand cleaning that meet the requirements in Env-A 1402.02(s)
  • Office activities, such as copying, duplication, typewriters, printers and blueprinting
  • Interior maintenance and janitorial activities, such as the use of cleaning products and air fresheners
  • Bathroom and locker room ventilation
  • Maintenance activities limited to welding, gluing, painting and soldering of process equipment
  • An air stripper or other equipment associated with soil venting that is used to remediate a petroleum or gasoline contaminated site that meets the requirements in Env-A 1402.02 (n)
  • Exterior grounds maintenance activities including lawn care and pest control
  • Food preparation activities (excluding activities connected to preparation of packaged food for off-site consumption)
  • Venting of particulate emissions from processes equipped with removal equipment and which are vented inside the building
  • Laboratory ventilation hoods for educational and research and development activities
  • The use of consumer products in a manner consistent with how the general public would use the products
  • The use of fire control equipment
  • Waste site characterization and feasibility tests in Env-A 1402.02 (r)



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