(4) How to wash the sampler.
Rinse in Di-ionized water, allow to dry on clean paper towel. DO NOT USE HEAT.
(5) What is the recommended sampling height?
2.5 meters or 8 feet.
(6) Transporting the Passive Sampler to the site.
After assembly, the loaded sampler is placed into the re-sealable plastic bag, the bagged sampler is placed into the brown airtight container provided and taken to the exposure site.
After exposure, the above procedure is again followed to safely seal the exposed sampler in the brown airtight vial. Once indoors and in a clean area, the exposed pad is placed in a shipping vial (PS-118). It is then taken or sent to a laboratory for analysis.
(7) How long can a loaded sampler be kept before it is used?
Once the sampler is loaded and placed in its airtight vial, it should be kept at standard room temperature, as long as it is to be taken on site within several days.
If the loaded sampler is not going to be used for several days, it is best to place it in a refrigerator (not a freezer). It should be removed from the refrigerator about 12 hours before exposure for the purpose of equilibrating to the room temperature. This is done to prevent condensation from forming on the pad. Moisture is the enemy of the coated pad, as it can remove some of the collecting material.
(8) To whom and where do you sell your product?
We also sell to Colleges and Universities and Government Agencies and other entities for air quality solutions all over the world including – The United States, Greece, China, South Africa, Belgium, Indonesia, India, Mexico, Romania, Australia, Canada, England, Korea, New Zealand and Nigeria.
(10) What is the ‘Control Pad’?
‘Control’ samplers are necessary for accurate results
A ‘Control’ sampler is a sampler that is loaded with a pre-coated pad from the same batch as the field samplers, and put in its brown airtight vial to be used as a ‘control’. This ‘control’ sampler should accompany the field samplers that are to be exposed, so that it is subject to the same temperatures and conditions as the others, but the control sampler should be kept in the brown vial (not exposed).
A batch of samplers consists of: (1) a ‘control sampler’ (never exposed) and (2) one or more field samplers (that are to be exposed), which share the same coating date, the same preparation date, the same handling, and preferably, the same analysis date.
Since the pre-coated filter pads are stored refrigerated before being loaded into samplers, all pads used for a designated batch must be removed from the refrigerated vial at the same time. Pads should be removed from the refrigerator about 12 hours before exposure for the purpose of equilibrating to the room temperatures. This is done to prevent condensation from forming on the pad. Moisture is the enemy of the coated pad, as it can remove some of the collecting material.
Samplers from the same batch are assembled, exposed, and disassembled over some period of time defined by the field study, but for the best results, the time period should not exceed four weeks. The ‘control’ sampler should be kept in the brown vial (not exposed). As much as is possible, keep the control and field samplers at the same approximate locations and temperature. When the sampling is completed, place the exposed samplers in the brown vial and keep at room temperature in a cool place until they are ready for analysis. This will minimize variation in the differences due to temperature effects within the batch. In a clean environment, remove the exposed field pads and ‘control’ unexposed pads from the samplers. It is best to do the analysis as soon as possible but can be done within 2 -3 weeks after exposure.
When the exposed pads and ‘control’ unexposed pads are sent to a lab to be analyzed, the ‘control’ pad is analyzed the same way as the field pads and clients will be billed for analysis of ‘control’ pad.
Further Instructions for filling out COC (Chain of Custody) Form that is to be sent to the lab with the exposed pads can be found on the Ogawa website, www.ogawausa.com, under the tab ‘Analysis Instructions/Form’.
(11) What is the storage time for the pre-coated pads?
If pads are sealed in original glass vial within the aluminum vacuum pack – 90 days in refrigerator or 1 year in freezer.
If pads are opened and unused ones resealed in vial – 90 days in refrigerator.
Loaded sampler in bag placed in brown vial with lid – 60 days in refrigerator.
Exposed loaded sampler, in bag placed in brown vial with lid – No refrigeration necessary as long as stored at normal room temperature, for no more than 14-21 days. The control pad must also be stored with exposed pads to detect any interference pads may accumulate during storage.
Note: Analysis should be done as soon as possible after exposure.
(12) Is there a certain refrigerated temperature to store the pads?
Not really, just the standard household refrigerator temperature. Note: Pads should be removed from the refrigerator about 12 hours before exposure for the purpose of equilibrating to the room temperatures. This is done to prevent condensation from forming on the pad. Moisture is the enemy of the coated pad, as it can remove some of the collecting material.
(13) Can NOx value alone be obtained by using one NOx pad?
The concentration of NOx cannot be obtained by just using one NOx pad.
NOx is a mixture of NO and NO2, so there is no alpha value for NOx.
We must use both NO2 and NOx pads simultaneously for sampling, and the two pads are then analyzed separately.
The concentrations obtained are then both used in the analytical formula shown in the protocol.
The calculation for NO is done by subtracting NO2 from NOx.
To determine the concentration of NOx, one must use one NO2 and one NOx pad on each side of same sampler.
(14) How many pads are needed for each type of sampling?
You will need one PS-100 sampler for every site and every gas that your customer wants to sample.
You can sample NO, NOx, NO2 with one sampler. NOx goes on one side and NO2 on the other side and then subtract the two to get NO.
You will use another sampler for O3, as it requires two collection pads to be used at the same time, one on each side of the sampler. The two pads are analyzed together.
You will use another sampler to do NH3, using 2 pads, one on each side of the sampler. The two pads analyzed together are considered one analysis.
(15) What are the exposure and collection times for the absorption?
Depending on concentration, from as little as 8 hours and up to 30 days. Ideally, no less than 24 hours.
(16) How long can an ‘exposed pad’ be kept?
Once the pad is exposed, it loses much of its sensitivity and can be stored in a normal room temperature for no more than 14-21 days. Naturally, the sooner the exposed pad is taken to the lab for analysis, the better. The coated pads are not affected by normal temperatures but should not be put in direct sunlight or in heated areas.
(17) Does Barometric pressure affect collection results?
As long as the calculations are for units of ppb, the passive sampler measurements are independent of barometric pressure, for any gas.
O3 ANALYSIS uses two O3 pads that are analyzed together, and is considered one analysis cost. NO Analysis uses one NOx pad and one NO2 pad on either end of the sampler.
NOx = NO2+NO and NO = NOx-NO2.
Each side is a separate analysis cost.
(21) What is the lowest detectable range?
| NO2 | 24 hr 2.3 ppb | 168 hr 0.32 ppb |
| NOx | 24 hr 2.3 ppb | 168 hr 0.37 ppb |
| SO2 | 24 hr 3.8 ppb | 168 hr 0.54 ppb |
| 03 | 24 hr 2.7 ppb | 168 hr 0.39 ppb |
| NH3 | 24 hr 2.3 ppb | 168 hr 0.32 ppb |
Please note that all the above ranges depend on the sensitivity of the analyzing instruments.
(22) What is the upper detectable range?
| NO2 | 24 hr < 25 ppm | 168 hr < 3.6 ppm |
| NOx | 24 hr 2 < 5 ppm | 168 hr < 3.6 ppm |
| SO2 | 24 hr < 25 ppm | 168 hr < 3.6 ppm |
| 03 | 24 hr < 0.8 ppm | 168 hr < 0.11 ppm |
| NH3 | 24 hr < 25 ppm | 168 hr < 3.6 ppm |
Please note that all the above ranges depend on the sensitivity of the analyzing instruments.
(23) What is the normal detectable range?
| NO2 | 24 hr 0-25 ppm | 168 hr 0- 3.6 ppm |
| NOx | 24 hr 0-25 ppm | 168 hr 0- 3.6 ppm |
| SO2 | 24 hr 0-25 ppm | 168 hr 0- 3.6 ppm |
| 03 | 24 hr 0-0.8 ppm | 168 hr 0-0.11 ppm |
| NH3 | 24 hr 0-25 ppm | 168 hr 0- 3.6 ppm |
Please note that all the above ranges depend on the sensitivity of the analyzing instruments.
(24) What is the response time (R.T.)?
Response Time = L2/2D = 0.9 (sec.)
Length (cm) D: Diffusion Coefficient (cm2/sec.20 Co)