paper 180 18 p analysis of ppb levels of photochemical smog components in air with a portable...

Analysis of PPB Levels of (VOC’s) Photochemical Smog Components in Air with a Portable Analyzer

Jennifer L. Maclachlan & Dr. J.N. DriscollPID Analyzers, LLC

Sandwich, MAPaper # 180 - 18P

Introduction• Wanted to test the feasibility of monitoring ambient air with a compact

multisensor PID based instrument like the Model 102+• Air monitoring networks are very complex and very expensive ($250K)

Is it possible to obtain useable data from an inexpensive portable analyzer?

• We used a PID for measuring VOC’s; a Dual beam IR sensor for CO2 and an electrochemical sensor for NO2

• We wanted to determine the effect of the weather on VOCs and other components in the air

• We are located on Cape Cod just off a highway (Rt 130) in Sandwich, MA

• We are across from Otis AFB which is part of the MMR that covers an area of 30 sq miles

Technology

• VOC’s- Photoionization- ppb 0-100,000

• CO2 – Infrared Absorbance- ppm 0-5,000

• NO2 – Electrochemical- > 50 ppb

PID-102+ with Multiple Sensors

Photoionization Process

PID Schematic

• R + hv = R + + e-

Dual Beam IR

CO2 Spectrum Schematic

Photo of Model 102 wSnap on Heads

PID-102+ uP, Amplifier & Sensor Boards

Sampling Location: Cape Cod, MA

Ambient Air Monitoring Cape Cod

Nearest home was ca 1 mile

Indoor Air Monitoring

Outside Air- Winter Day

Outside Air- Raining

Outside Air- Snowy Day

NO2 ppb

Comparison of Weather Conditions on VOC Concentrations

Type of day Morning Afternoon

Winter < 10 ppb < 10 ppb

Rainy < 10 ppb 35-70 ppb

Snowy < 10 ppb 35-100 ppb

Summary• A portable multisensor instrument like the Model 102+ can be

used to provide valuable info on where to site VOC “hot spots” for future air monitoring stations

• The analyzer could be enclosed in a weather proof enclosure and mounted on a telephone pole with bluetooth capability for remotely collecting data

• Weather (rain or snow) does affect the VOC levels significantly as expected and the 102+ was able to detect this effect

• The NO2 sensor selected was not sensitive enough to measure ambient levels of NO2

• The PID and IR will work in this environment but other ppb level sensors are needed to complement the Model 102