There are six categories of thresholds. Three thresholds relate to the use of substances, one to nutrient emissions to water, and two to fuel combustion or energy use. More details are in the NPI Guide and the NEPM for the NPI .

Category 1a threshold relates only to Total Volatile Organic Compounds (Total VOCs) when a facility uses 25 tonnes or more of VOCs. That is bulk storage facility, uses 25 tonnes or more of VOCs and has a 25 kilotonne or greater design storage capacity for material containing VOCs.

To make a Category 1a determination, a facility must calculate and sum the tonnage of all VOCs used on site, both as individual substances and as constituents of other substances (such as fuel). While a facility may not have used enough of any single NPI substance that is a VOC to trip individual thresholds, they may have used enough VOCs in total to trip the Category 1a threshold for Total VOCs.

For example, a facility uses 400 tonnes of heating oil that consists of 12 weight percent VOCs and 88 weight percent of other substances; i.e. the facility has used 48 tonnes of VOCs. This clearly trips the category 1a threshold and, therefore, Total VOCs must be reported.

Note: a facility may also need to report on the individual NPI substances that are VOCs if their usage trips other reporting thresholds. (See also Calculating Thresholds, Definition of VOCs and double counting.)

In such circumstances, the occupier should take the mid-point of the range advised on the MSDS as the relevant figure for threshold calculations.

If your facility has exceeded a NPI substance threshold and you can't apply an emission factor or other emission estimation technique, your state or territory environment agency should be consulted.

Data is displayed on the NPI database to two significant figures. This means that facilities are required to report emissions to air, land and water to a precision of two significant figures. If the third significant figure is a 5, the second figure is rounded to the closest even number (for example 12.5 is rounded to 12 and 13.5 is rounded to 14) as outlined in Australian Standard 2706 - 1984.

If the NPI substance emission is required to be reported because a threshold is exceeded and emission is estimated to be zero, then you should report the figure '0' to the NPI.

An indication that a listed substance is below detection limit is not the same as stating that the substance is not present. If the best available information indicates no presence of a substance in the waste-stream, a facility may report zero. The facility should document that it considered available data in making this determination.

If, based on best available information, there is reason to believe that the listed substance is likely to be present in the waste-stream, a concentration equivalent to half of the detection limit should be used in the estimated emission calculation.

In all cases, the less than detection limit measurement should be based on the most accurate or appropriate methodology readily available for analysis of the listed substance. Acceptable use of zero in these situations is always at the discretion of the relevant state or territory environment agency.

No. The NPI requires the reporting of estimated emissions — that is, emissions from a facility that are calculated using an accepted EET. Facilities should always report a specific emission amount arrived at through the use of an EET.

If the electronic tool is based on the EET in an NPI EET Manual and is transparent in its estimation method, it will be classified as an approved EET. If the estimation method is not transparent, then the tool needs to be submitted to the relevant state or territory environment agency for approval.

Explosives are classed as fuel for the purposes of NPI reporting threshold calculations. The total mass of the explosive is to be included in the calculation (e.g. total mass of ammonium nitrate/fuel oil mixture, not just the fuel oil component).

Category 1 substances contained in mined ore or waste (including overburden) should be included in NPI reporting threshold calculations. For example, Category 1 substances in material moved to a waste dump landfill are to be taken into account when determining a facility's use of a NPI substance. See the NPI Guide for more information.

The placing of a substance on the waste dump landfill is not regarded as an emission of the substance to the environment. Any loss of an NPI substance from the waste dump landfill is regarded as an emission (e.g. escaping in leachate or as wind-blown particulate matter) and if the NPI substance reporting threshold is tripped, it must be reported.

Tailings are sludge, mineral residue and wastewater (apart from final effluent) resulting from ore extraction or processing. In some cases this may be the slag from pyrometallurgical processes. Tailings vary widely in properties and constituents depending on the mineral being processed and the extraction process used. This means that the environmental impact and human health effects of tailings also vary widely.

In some industries the term tailings is being replaced by other terms to more accurately reflect the nature of the material. Any future change in terminology the NPI uses will reflect the terminology that industry and other sectors of the community use.

Yes. Any spills or leakages that lead to an emission to the environment to air, land or water must be reported if a reporting threshold is tripped.

Many industries use buffer zones to decrease their impact on neighbouring communities.

Buffer zones do not decrease the emissions of a substance, but they do allow additional substance dispersion prior to crossing the facility boundary. In some cases, particulate material settling may occur within the buffer zone. A buffer zone can also provide a facility with the opportunity to monitor, or take action to control emissions before release beyond the facility boundary.

If combustion processes and/or sources trip a PM₁₀ threshold, all the facility PM₁₀ emissions from all sources must be reported. For example, in addition to combustion sources, PM₁₀ emissions generated from stockpiles need to be included.

No. This is because the substances on the NPI substance list are not always mutually exclusive. For example, pollutants such as PM₁₀ and VOCs are aggregate substance groups that may comprise the emissions of other substances reported to the NPI.

If emissions of individual Volatile Organic Compounds (VOCs), such as benzene, exceed their reporting thresholds, you will need to report them separately as well as reporting 'Total Volatile Organic Compounds' if the threshold for TVOCs is exceeded (See definition of Total VOCs).

These facilities should report to the NPI. The main substance expected to be reported is TVOCS. Some states and territories may require valve stations reports from by the facility. Contact the state or territory to determine if reporting is required.

Generally you can estimate zero emissions of fluoride compounds from natural gas and LPG combustion. An exception may be where a facility operator knows that fluoride compounds or fluorine are in the natural gas or LPG they use, or if the methods of using these fuels are likely to result in emissions e.g. in a cement kiln. Check with your supplier and refer to your NPI industry sector manual for more details.