Sampling and analysing air emissions

NSW industries and commercial premises can ensure they comply with NSW air quality regulations by sampling and analysing their emissions of air pollutants.

Approved methods for the sampling and analysis of air pollutants (AMSAAP) (PDF 160KB) lists the methods that must be used to sample and analyse

  • air pollutant emissions from stationary industrial and commercial premises
  • pollutant emissions from motor vehicles
  • components in, and properties of, petroleum products
  • pollutants in ambient air

The methods specified in AMSAAP are referred to in

Find out more about relevant legislation and compliance [link to ‘Industrial emissions’ page]

Find out more about AMSAAP.

This page provides information about sampling and analysis that is not available in AMSAAP.

Always use the approved sampling and analysis methods unless your licence condition specifically requires or allows for the use of alternatives. You can apply to use alternative methods in 'exceptional circumstances'. Your application must establish

  • the circumstances that justify using an alternative method
  • the underpinning case for the method you propose to use

For more information see section 1 of AMSAAP.

Suitable locations to take a stack sample

Approved method AS 4323.1-1995 (the Standard) can be used at all industrial premises under all circumstances. However, USEPA Method1 is an alternative approved method suitable for use under approved circumstances, as outlined in Section 2 of the AMSAAP.

The Standard outlines two considerations for locating a suitable sampling plane: physical location and characteristics for suitable gas flow.

Location criteria

The further the sampling plane is from a disturbance to emission gas flow, such as a bend or a fan, the more suitable the gas flow characteristics will be for sampling. The Standard specifies how close to a flow disturbance a sampling plane can be located.

Two types of sampling plane location are described in the Standard.

  • An 'ideal sampling plane' complies with the minimum distances specified in Table 1 of the Standard and must be used if it is available.
  • A 'non-ideal sampling plane' is closer to a flow disturbance than specified in Table 1, but uses an increased number of sampling points to compensate for the disturbance, as specified in Table 2 of the Standard.

Both these types of sampling planes comply with the Standard.

A third type of sampling plane can be inferred which does not comply with the Standard because it is too close to a disturbance to allow reliable measurement. A non-compliant sampling plane

  • is closer than one duct diameter upstream of a bend, or
  • is closer than two duct diameters downstream of a bend, or
  • does not meet criteria (a) to (f) in section 4.1 of the Standard

As location criteria in the Standard cannot be met in many existing industrial stacks, section 2 of AMSAAP specifies approved circumstances in which USEPA Method 1 can be used instead.

USEPA Method 1 provides for sampling in a location that is sufficiently close to a flow disturbance that it would be considered non-compliant with the Standard. However, this method is acceptable only if it can be demonstrated that certain gas flow criteria can be achieved.

Flow criteria describe

  • gas flow direction
  • velocity
  • flow profile across the duct
  • temperature and pressure characteristics of the gas stream

These criteria must be met for a sampling location to comply with the Standard.

Considerations when upgrading or renewing equipment

Upgrading or renewing equipment generally provides an opportunity to ensure a sampling plane compliant with the Standard is made available. For example, if the work includes replacing the existing stack, the new stack could be constructed to have features that comply with the Standard.

However, if the work is limited to upgrading equipment upstream of the emission point but retains the existing emission stack infrastructure, the sampling position requirements remain the same as for the existing infrastructure.

AMSAAP nominates methods for sampling and analysing hydrogen sulfide in stack emissions. The methods vary in certain ways, including sensitivity of detection. USEPA Method 11 is a cost-effective method for sampling and analysing hydrogen sulfide in stack emissions, but may not be sensitive enough to demonstrate regulatory compliance. However, there is scope to improve the sensitivity.

The nominal sampling time of at least 10 minutes can be legitimately increased to allow capture of hydrogen sulfide from an increased gas stream volume. This reduces the low limit of detection. However, care is needed to ensure that the capture solutions are not saturated during the increased sampling time.

This modification is considered to be within the scope of the method and does not need approval by the EPA.

Approved method USEPA Method 7E requires a sample to be continuously extracted from the gaseous stream and a fraction of this conveyed to an instrumental analyser which determines the concentrations of nitric oxide (NO) and oxides of nitrogen (NOx). The method nominates use of a chemiluminescence analyser. However, as noted under TM-11 of AMSAAP, the EPA recognises the use of any appropriate instrumental analyser for this purpose, provided the performance specifications of USEPA Method 7E are met to ensure reliable data.

Following from this, the concentration of NO2 can be calculated as the difference between measured NO and NOx. This data can be reported directly or, if required, converted into an equivalent NO2 concentration. Details of these calculations are given in Appendix I of AMSAAP.

Odour is expressed as a concentration, and is represented as a number of 'odour units' (OU). One OU is defined as the minimum concentration of the substance that causes a positive physiological response in a reference panel of individuals.

Cycling times and data recording requirements 

  • For opacity – minimum of 1 cycle of sampling and analysis for each successive 10-second period and 1 cycle of data recording for each successive 6-minute period.
  • For all CEM systems except opacity – minimum of 1 cycle of operation (sampling, analysis and data recording) for each successive 15-minute period. 

Averaging period requirements 

Except as otherwise specified in the relevant environment protection, the averaging periods to be used are

  • for opacity, all data must be reduced to 6-minute averages calculated from 36 or more data points equally spaced over each 6-minute period
  • for all CEM systems except opacity, all data must be reduced to 1-hour averages calculated from 4 or more data points equally spaced over each 1-hour period

Monitor downtime 

As a guide, the minimum data capture for opacity monitoring should be 95%, and for all other CEM systems, 90%. This allows a reasonable period of monitor downtime in the following situations

  • monitor breakdown
  • scheduled monitor maintenance
  • daily zero and span checks
  • performance specification testing

Calculating emissions from combined sources

A licensed pulp and paper mill is operating

  • a lime kiln fired on timber waste
  • a kraft recovery boiler fired on solid fuel (boiler 1)
  • a gas-fired power boiler (boiler 2)

all of which discharge through a single main stack. Each emission unit belongs to Group 6 under the Regulation.

What is the oxides of nitrogen standard of concentration and reference oxygen concentration for the main stack if all three emission units are operating?

The applicable standards of concentration for emission of oxides of nitrogen (NOx) for each individual emission unit are specified in Schedule 3 of the Protection of the Environment Operations (Clean Air) Regulation, under 'Paper, paper pulp or pulp products industries'. The oxygen reference level that applies to each emission unit is specified in Schedule 5, Part 3 of the Regulation. The volumetric flow rate of each emission unit is also known. This information is summarised below:

Emission unit

NOx standard of concentration (CN) (mg/Nm3)

Oxygen reference concentration (ON) (%)

Volumetric flow rate (qN) (Nm3/s)

Boiler 1 (solid fuel)

300

7

35

Boiler 2 (gas fuel)

300

3

50

Lime kiln (solid fuel)

400

7

5

The alternative standard of concentration for a combined source (Cr) is calculated as follows:

(1)

C1q1 + C2q2 + ........ + CN qN
Cr =  _________________________
             q1 + q2 + ........ + qN

where

C= the standard of concentration applicable to the Nth emission unit
 qN  =  
the volumetric flow rate of the Nth emission unit

Using Equation 1, the oxides of nitrogen alternative standard of concentration for the main stack is

Cr =    300 x 35 + 300 x 50 + 400 x 5 
            35 + 50 + 5

=   27500 
     90

= 305.5

= 306 mg/Nm3 rounded to the nearest integer


The reference oxygen concentration for a combined source (Or ) is calculated as follows

(2)

O1q1 + O2q2 + ........ + ON qN
Or =  _________________________
             q1 + q2 + ........ + qN

where

O =  the reference oxygen concentration applicable to the Nth emission unit
 qN 
=  the volumetric flow rate of the Nth emission unit

 Using Equation 2, the reference oxygen concentration for the main stack is

Cr =    7 x 35 + 3 x 50 + 7 x 5 
                   35 + 50 + 5 

=   430 
     90

= 4.77%

= 5% rounded to the nearest integer

305.5 mg/Nm3 @ 4.77% O2 = 305.5 x    (21 - 5)    = 301 mg/Nm3 @ 5% O2                   
   (21 - 4.77)

The oxides of nitrogen standard of concentration for the main stack, when all three emission units are operating, is 301 mg/Nm3 @ 5% O2

What are the oxides of nitrogen standard of concentration and reference oxygen concentration for the main stack if boiler 1 is shut down?

Using Equation 1, the oxides of nitrogen alternative standard of concentration for the main stack is calculated assuming CN  and  qN  for boiler 1 is zero        

Cr =   300 x 50 + 400 x 5

50 + 5

=   17000

55

= 309.1

= 309 mg/Nm3 rounded to the nearest integer

Using Equation 2, the reference oxygen concentration for the main stack is

Cr =   3 x 50 + 7 x 5

50 + 5

= 3.36%

= 3% rounded to the nearest integer

 

309.1 mg/Nm3 @ 3.36% O2 = 309.1 x    (21 - 5)    = 315 mg/Nm3 @ 5% O2                   

(21 - 3.36)

The oxides of nitrogen standard of concentration for the main stack when boiler 1 is shut down is 315 mg/Nm3 @ 3% O2

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